Problems and Applications

Chapter 13
Problems and Applications

1. a. opportunity cost; b. average total cost; c. fixed cost; d. variable cost; e. total cost; f. marginal cost.

2. a. The opportunity cost of something is what must be given up to acquire it.

b. The opportunity cost of running the amulet store is $430,000, consisting of $350,000 to rent the store and buy the stock and a $80,000 implicit cost, because Buffy would quit her job as a vampire hunter to run the store.

3. 
   $400,000 - $350,000 = $50,000
   

3. 
   Because the total opportunity cost of $430,000 exceeds the projected revenue of $400,000, Buffy should not open the store, as her economic profit would be negative.
   

3. 
   Greater than $430,000.
   

3. a. The following table shows the marginal product of each hour spent fishing:

Hours	Fish	Fixed Cost	Variable Cost	Total Cost	Marginal Product
0	0	$10	$0	$10	---
1	10	10	5	15	10
2	18	10	10	20	8
3	24	10	15	25	6
4	28	10	20	30	4
5	30	10	25	35	2

b. Figure 7 graphs the fisherman's production function. The production function becomes flatter as the number of hours spent fishing increases, illustrating diminishing marginal product.

Figure 7

c. The table shows the fixed cost, variable cost, and total cost of fishing. Figure 8 shows the fisherman's total-cost curve. It has an upward slope because catching additional fish takes additional time. The curve is convex because there are diminishing returns to fishing time because each additional hour spent fishing yields fewer additional fish.

Figure 8

4. Here is the completed table:

Workers	Output	Marginal Product	Total Cost	Average Total Cost	Marginal Cost
0	0	---	$200	---	---
1	20	20	300	$15.00	$5.00
2	50	30	400	8.00	3.33
3	90	40	500	5.56	2.50
4	120	30	600	5.00	3.33
5	140	20	700	5.00	5.00
6	150	10	800	5.33	10.00
7	155	5	900	5.81	20.00

a. See the table for marginal product. Marginal product rises at first, then declines because of diminishing marginal product.

b. See the table for total cost.

c. See the table for average total cost. Average total cost is U-shaped. When quantity is low, average total cost declines as quantity rises; when quantity is high, average total cost rises as quantity rises.

d. See the table for marginal cost. Marginal cost is also U-shaped, but rises steeply as output increases. This is due to diminishing marginal product.

e. When marginal product is rising, marginal cost is falling, and vice versa.

f. When marginal cost is less than average total cost, average total cost is falling; the cost of the last unit produced pulls the average down. When marginal cost is greater than average total cost, average total cost is rising; the cost of the last unit produced pushes the average up.

5. At an output level of 600 consols, total cost is $180,000 (600 × $300). The total cost of producing 601 consols is $180,901. Therefore, you should not accept the offer of $550, because the marginal cost of the 601st consol is $901.

6. a. The fixed cost is $300, because fixed cost equals total cost minus variable cost. At an output of zero, the only costs are fixed cost.

b.

Quantity__Variable_Cost__Fixed_Cost__Total_Cost'>Quantity__Total_Cost__Variable_Cost__Marginal_Cost_(using_total_cost)'>Quantity	Total Cost	Variable Cost	Marginal Cost (using total cost)	Marginal Cost (using variable cost)
0	$300	$0	---	---
1	350	50	$50	$50
2	390	90	40	40
3	420	120	30	30
4	450	150	30	30
5	490	190	40	40
6	540	240	50	50

Marginal cost equals the change in total cost for each additional unit of output. It is also equal to the change in variable cost for each additional unit of output. This relationship occurs because total cost equals the sum of variable cost and fixed cost and fixed cost does not change as the quantity changes. Thus, as quantity increases, the increase in total cost equals the increase in variable cost.

7. The following table illustrates average fixed cost (AFC), average variable cost (AVC), and average total cost (ATC) for each quantity. The efficient scale is 4 houses per month, because that minimizes average total cost.

Quantity	Variable Cost	Fixed Cost	Total Cost	Average Fixed Cost	Average Variable Cost	Average Total Cost
0	$0.00	$200.00	$200.00	---	---	---
1	10.00	200.00	210.00	$200.00	$10.00	$210.00
2	20.00	200.00	220.00	100.00	10.00	110.00
3	40.00	200.00	240.00	66.67	13.33	80.00
4	80.00	200.00	280.00	50.00	20.00	70.00
5	160.00	200.00	360.00	40.00	32.00	72.00
6	320.00	200.00	520.00	33.33	53.33	86.67
7	640.00	200.00	840.00	28.57	91.43	120.00

8. a. The lump-sum tax causes an increase in fixed cost. Therefore, as Figure 10 shows, only average fixed cost and average total cost will be affected.

Figure 10

b. Refer to Figure 11. Average variable cost, average total cost, and marginal cost will all be greater. Average fixed cost will be unaffected.

Figure 11
9. a. The following table shows average variable cost (AVC), average total cost (ATC), and marginal cost (MC) for each quantity.

Quantity	Variable Cost	Total Cost	Average Variable Cost	Average Total Cost	Marginal Cost
0	$0.00	$30.00	---	---	---
1	10.00	40.00	$10.00	$40.00	$10.00
2	25.00	55.00	12.50	27.50	15.00
3	45.00	75.00	15.00	25.00	20.00
4	70.00	100.00	17.50	25.00	25.00
5	100.00	130.00	20.00	26.00	30.00
6	135.00	165.00	22.50	27.50	35.00

b. Figure 12 shows the three curves. The marginal-cost curve is below the average-total-cost curve when output is less than four and average total cost is declining. The marginal-cost curve is above the average-total-cost curve when output is above four and average total cost is rising. The marginal-cost curve lies above the average-variable-cost curve.

Figure 12

10. The following table shows quantity (Q), total cost (TC), and average total cost (ATC) for the three firms:

	Firm A		Firm B		Firm C
Quantity	TC	ATC	TC	ATC	TC	ATC
1	$60.00	$60.00	$11.00	$11.00	$21.00	$21.00
2	70.00	35.00	24.00	12.00	34.00	17.00
3	80.00	26.67	39.00	13.00	49.00	16.33
4	90.00	22.50	56.00	14.00	66.00	16.50
5	100.00	20.00	75.00	15.00	85.00	17.00
6	110.00	18.33	96.00	16.00	106.00	17.67
7	120.00	17.14	119.00	17.00	129.00	18.43

Firm A has economies of scale because average total cost declines as output increases. Firm B has diseconomies of scale because average total cost rises as output rises. Firm C has economies of scale from one to three units of output and diseconomies of scale for levels of output beyond three units.

Chapter 14