A firm’s average total cost of production is Rs.300 at 5 units of output and Rs.320 at 6 units of output. The marginal cost of producing the 6th unit is

The correct answer is A. Rs.20.

Marginal cost is the change in total cost that arises when one additional unit of output is produced. In this case, the firm’s average total cost of production increases from Rs.300 to Rs.320 when it produces 6 units of output. This means that the marginal cost of producing the 6th unit is Rs.20.

Option B is incorrect because it is the average total cost of production, not the marginal cost. Option C is incorrect because it is the total cost of producing 6 units of output, not the marginal cost. Option D is incorrect because it is the total cost of producing 5 units of output, not the marginal cost.