Suppose that for a particular firm the only variable input into the product process is labor and that output equals zero when no workers are hired. In addition, suppose that marginal cost of the third worker hired is $40, and the average total cost when three workers are hired is $50. What is the total cost of production when three workers are hired?

Answer: The correct answer is $150.

Explanation:

We know that the marginal cost of hiring a third worker is $ 40. And that the average total cost when 3 workers are hired is $ 50. The average total cost formula is:

Average total cost = (total cost) : (number of workers)

Then we solve the equation in 3 steps:

1) $ 50 = X : 3

2) $ 50 * 3 = X

3) $ 150 = X

We can diagram the workers cost chart

Number of workers - Marginal cost - Total cost

1 - $60 - $60

2 - $50 - $110

3 - $40 - $150