Consider the cost data: Output (Q): 0, 1, 2, 3, 4, 5, 6 and Total Cost (₹): 240, 330, 410, 480, 540, 610, 690. What is the marginal cost of the 6th unit of output?

1. MC of the 6th unit = TC₆ − TC₅. 2. TC₆ = ₹ 690 and TC₅ = ₹ 610. 3. MC = 690 − 610 = ₹ 80. 4. ₹ 70 (A) is the MC of the 5th unit (610−540), ₹ 115 (B) is ATC at 6 units (690/6 = 115), and ₹ 690 (D) is total cost, not the increment. Hence ₹ 80. _Source: ICAI BoS CA Foundation Paper 4 Business Economics, Ch 3 Unit II "Theory of Cost", p.19_