The only variable input a janitorial service firm uses to clean offices is workers who are paid a wage, w, of $8 an hour. Each worker can clean four offices in an hour. Use math to determine the variable cost, the average variable cost, and the marginal cost of cleaning one more office. Draw a diagram similar to Figure 7.1 to show the variable cost, average variable cost, and marginal cost curves?
Figure 7.1: Short-Run Cost Curves

15 VC 1,725 160 800 450 Quantity, q. Units per day 10 15 MC 125 115 AC AVC 80 45 AFC 10 15 Quantity, q. Units per day Cost per unit, $ Cost, $