Explanation: (B) Arif's rate (\(R_A\)): \(\frac{1}{12}\) of the work per hour. Work remaining = \(1 - \frac{2}{3} = \frac{1}{3}\). Babu's rate (\(R_B\)): 20% of Arif's rate = \(0.20 \cdot R_A = \frac{1}{5} \cdot \frac{1}{12} = \frac{1}{60}\) of the work per hour. Time for Babu to finish the remaining \(\frac{1}{3}\) work: \(T_B = \frac{\text{Work}}{\text{Rate}_B} = \frac{1/3}{1/60} = \frac{1}{3} \cdot 60 = 20 \text{ hours}\).
