Chapter 16 – The Demand for Resources
16-8
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Answer: a. To answer this question we begin by finding the ratios of the marginal product of
each input to their respective prices for the first unit of each input.
Capital (unit 1): 24/3=8 Labor (unit 1): 11/1=11
Since the ratio is larger for labor we employ the first unit of labor giving us 11 units of output.
The next step is to calculate the marginal product of labor to price ratio for the second unit of
labor and compare this with the first unit of capital (which we did not select in the first step).
Capital (unit 1): 24/3=8 Labor (unit 2): 9/1=9
Since the ratio is once again larger for labor we employ the second unit of labor giving us an
additional 9 units of output and a total of 20 (=11 (for the first unit of labor) + 9 (for the second
unit of labor)) .
We continue the process comparing the third unit of labor with the first unit of capital.
Capital (unit 1): 24/3=8 Labor (unit 3): 8/1=8
Here they are equal so we could choose either, or in this case both, to increase output. Since we
now employ the first unit of capital we add 24 units to our total and the third unit of labor adds 8.
This gives is a total of 52 (= 20 (from above) + 24 +8).
Since we are still not at 80 units of output, we continue on down the marginal product of labor
and capital schedules choosing inputs based on the algorithm above.
We will end up employing 2 units of capital and 4 units of labor (the next step in the process
above).
Capital (unit 2): 21/3=7 Labor (unit 4): 7/1=7
Total output is 80 (=52 (from above) + 21 (unit 2 of capital) +7 (unit 4 of labor))
Thus, the least-cost combination is found by equating the marginal product of each input to their
respective prices. Or, employ the product that costs less per unit of output.
b. To determine the profit maximizing combination of inputs we use the same process above,
except we now need to calculate total cost, total revenue, and profit.
The first step gave us 1 unit of labor and 0 units of capital with 11 units of output. Total revenue
equals $11 and total cost equals $1, which gives us $10 in profit.
Step 2 gave us 2 units of labor and 0 units of capital with 20 units of output. Total revenue equals
$20 and total cost equals $2, which gives us $18 in profit.
Step 3 gave us 3 units of labor and 1 unit of capital with 52 units of output. Total revenue equals
$52 and total cost equals $6 (=$3 (capital) + $3 (3 units of labor)), which gives us $46 in profit.
Continuing on, Step 4 gives us 4 units of labor and 2 units of capital with 80 units of output. Total
revenue equals $80 and total cost equals $10, which gives us $70 in profit.
This process will continue until we reach 7 units of labor and 7 units of capital with 142 units of
output. Total revenue equals $142 and total cost equals $28, with a profit of $114. You can verify
that profit falls adding one more unit of capital or labor.
A less time intensive approach is to recognize that the Marginal Revenue Product (MRP) for
labor and capital equal their respective Marginal Product schedules since the price of each unit of
output is $1. Profit maximization occurs where the Marginal Resource Cost (MRC) equals
Marginal Revenue Product (MRP). Since the MRC is $3 for capital and $1 for labor, equate these
values with the MRP for capital and labor. This occurs at 7 units of capital (MRP=$3=MRC) and
7 units of labor (MRP=$1=MRC). This rule is MRPL/PL = MRPK/PK =1.
Finally, since MPL/PL = MPL/PL for profit maximization the least-cost rule also applies.