Table 13-3 Number of Fixed Variable Total Workers Output Cost Cost Cost O O $50 $50 90 $50 $20 $70 170 $50 $40 $90 AWN 230 $50 $60 $110 240 $50 $80 $130 45. Refer to Table 13-3. The marginal product of the fourth worker is a. 10 units. b. 60 units. c. 230 units. d. 240 units