Use figure 7.8 to answer the following question: Figure 7.8 Cost (S) 50 40 ATC AVC 30 25 20 18 10 10 20 30 40 50 60 70 80 90 100 Quantity of output (units) (Figure 7.8) The average fixed cost at 70 units of output is cost of production is _, and the firm's fixed a) $43; $3,010 b) $11; $560 c) $0.10; $7 d) $7; $490