Labor costs represent a large percentage of total costs for many firms. According to data from the Bureau of Labor Statistics, U. S. labor costs were up 2.0% in 2015, compared to 2014.

a. When labor costs increase, what happens to average total cost and marginal cost? Consider a case in which labor costs are only variable costs and a case in which they are both variable and fixed costs. An increase in labor productivity means each worker can produce more output. Recent data on productivity show that labor productivity in the U. S. nonfarm business sector grew by 1.7% between 1970 and 1999, by 2.6% between 2000 and 2009, and by 1.1% between 2010 and 2015.
b. When productivity growth is positive, what happens to the total product curve and the marginal product of labor curve? Illustrate your answer with a diagram.
c. When productivity growth is positive, what happens to the marginal cost curve and the average total cost curve? llustrate your answer with a diagram.
d. If labor costs are rising over time on average, why would a company want to adopt equipment and methods that increase labor productivity?