Option 1 -> At output 2, MC = 15 = Price, but MC is falling afterward (drops to 10 at output 3), so not profit-maximizing.
Option 2 -> At output 3, MC = 10 < Price (15), so the firm should continue producing more units.
Option 3 -> At output 5, MC = 15 = Price, and MC is rising (from 12 to 15), satisfying the profit-maximizing condition.
Option 4 -> At output 6, MC = 24 > Price (15), so producing this unit reduces profit.
Hence, Option 3 (Output = 5) -> A perfectly competitive firm maximizes profit where MC = Price and MC is rising. At output 5, MC equals the price (Rs 15), and the marginal cost is increasing from the previous unit (MC was 12 at output 4). This ensures the firm is at the optimal production level where the last unit produced adds exactly as much to revenue as it does to cost. -> correct