The short-run average total cost curve (ATC_SR,20) and the long-run average total cost curve (ATC_LR) are constructed using TC_SR and TC_LR from Figure 7.6. At Y, when Q = 20 and the cost-minimizing amount of capital is 6 units, the ATC_SR and ATC_LR both equal $9. At all other values of Q, including Q = 10 and Q = 30, ATC_SR is above ATC_LR, and short-run average total cost is higher than long-run average total cost.