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Problem:

Suppose a firm's short-run total product schedule is given in the table below. It sells its output competitively for $1.50 each.

Labor
Total Product
Marginal Product
Marginal Revenue Product
0
0
  
1
8
  
2
18
  
3
29
  
4
39
  
5
47
  
6
52
  
7
53
  
8
53
  
  1. What is the marginal product of the 1st worker?
  2. What is the marginal revenue product of the first worker?
  3. Suppose the wage is $7. How many workers will this firm hire?
  4. If the wage rises to $9, how will the firm adjust its employment?
  5. Alternatively, suppose the firm sells its output according to the following demand schedule:
    Labor
    Total Product
    Product Price
    Marginal Product
    Marginal Revenue Product
    0
    0
    ----
    1
    8
    $ 3.50
    2
    18
    2.80
    3
    29
    2.30
    4
    39
    1.90
    5
    47
    1.65
    6
    52
    1.50
    7
    53
    1.40

Fill in the remaining two columns of the table. How many workers will be hired at a wage of $7?

Answer:

  1. Marginal product is the addition to total output associated with the next worker. Total output rises from 0 to 8 with the addition of the first worker, so the marginal product is 8.
  2. Marginal revenue product is the increase in total revenue associated with the next worker. For a competitive, this is product price times marginal product. The marginal revenue product of the first worker is $12. $12 = $1.50 x 8.
  3. To determine the profit-maximizing level of employment, it is necessary to find marginal revenue product and compare it to the wage rate. The completed table is below:
    Labor
    Total Product
    Marginal Product
    Marginal Revenue Product
    0
    0
      
    1
    8
    8
    $ 12.00
    2
    18
    10
    15.00
    3
    29
    11
    16.50
    4
    39
    10
    15.00
    5
    47
    8
    12.00
    6
    52
    5
    7.50
    7
    53
    1
    1.50
    8
    53
    0
    0.00
    Maximum profits are obtained by hiring only those workers whose marginal revenue products exceed the wage. In this example, 6 workers are hired.
  4. The 6th worker is no longer profitable. Reducing employment revenue. Maximum profits requires 5 workers.
  5. The completed table is shown below:
    Labor
    Total Product
    Product Price
    Marginal Product
    Marginal Revenue Product
    0
    0
    ----
    1
    8
    $ 3.50
    $ 28.00
    $ 28.00
    2
    18
    2.80
    50.40
    22.40
    3
    29
    2.30
    66.70
    16.30
    4
    39
    1.90
    74.10
    7.40
    5
    47
    1.65
    77.55
    3.45
    6
    52
    1.50
    78.00
    .45
    7
    53
    1.40
    74.20
    -3.80
    Comparing MRP to the wage, the firm maximizes profits by hiring 4 workers.


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Problem:

Suppose a firm's marginal product of capital and marginal product of labor schedules are as shown in the table below. The firm hires both capital and labor competitively for $4 and $8, respectively. Its output is sold competitively for $.50 each.

Capital
MP of Capital
Labor
MP of Labor
0
0
1
10
1
28
2
9
2
30
3
8
3
24
4
7
4
20
5
6
5
16
6
5
6
12
7
4
7
8
8
3
9
4
  1. Suppose the firm is currently using 4 units of capital and 4 units of labor. Is the corresponding output being produced at least cost? How do you know?
  2. What is the profit-maximizing combination of labor and capital the firm should use?
  3. What output level corresponds to the input combination you just found? Is this the least-costly combination of labor and capital to produce this level of output?
  4.  

Answer:

  1. No. The marginal product of the fourth unit of capital is 7, and its marginal product per dollar is 1.75 = 7/$4. The marginal product of the fourth worker is 20, and her marginal product per dollar is 2.50 = 20/$8. Labor is more productive per dollar, implying that the same output level could be produced more cheaply using relatively more labor and less capital.
  2. Find the marginal revenue products of both capital and labor by multiplying their respective marginal products by the output price. At the profit-maximizing output level, each of these should be equal to their respective prices (MRPK/PK = MRPL/PL = 1). The relevant table is reproduced below:
    Capital
    Labor
    MRPK/PK
    MRPL/PL
    0
    0
     
    1
    1
    1.25
    1.75
    2
    2
    1.125
    1.875
    3
    3
    1
    1.5
    4
    4
    0.875
    1.25
    5
    5
    0.75
    1
    6
    6
    0.625
    0.75
    7
    7
    0.5
    0.5
    8
    9
    0.375
    0.25
  3. For example, the MRP of the first unit of capital is PxMPK = $.50x10 = $5. Since the price of capital is $4, MRPK/PK = 5/4 = 1.25. Since this is greater than 1, the firm will expand its use of capital. The firm should use 3 units of capital and 5 units of labor.

  4. Total output is found by accumulating the marginal products of capital and labor: Output = 7+9+8+28+30+24+20+16 = 142. Since the marginal product per dollar of each input is the same, this is the least cost combination of resources.







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