The cost of a firm has increased from Rs. 67 to Rs. 80 when the units of cotton production rose from 8 to 9. Calculate the marginal cost of a firm?

Rs. 13

The correct answer is Option (2) → Rs. 13 

• Change in Total Cost = Rs. 80 − Rs. 67 = Rs. 13

• Change in Output = 9 − 8 = 1 unit

Marginal Cost=Δ Total Cost/ Δ Output  = 13/ 1 = 13