I cannot figure out how to calculate Marginal cost. I understand how to find Average cost.

of production. Labor Shirts Total Marginal Fixed Cost Variable Total Average Marginal Revenue Revenue Cost Cost Total Cost Cost 40 $200 $5 $75 $20 $95 SO.50 2 $340 $5 $75 $115 $1.69 $0.71 95 5475 $75 $135 $1.42 120 $600 $75 $155 $1.29 50 80 The average cost at the first level of production is The marginal cost at the third level of production is