Correct answer is (c) 32
The explanation is: The given ratio of radii = 5:3; \(\frac {R2}{R1} = \frac {5}{3}\) → R2 = \((\frac {5}{3})\) R1
R1 = 12 ohms (given); R2 = \(( \frac {5}{3} )\) × 12 = 20 ohms. So, R1 = 12 ohms and R2 = 20 ohms
Therefore, total resistance (R) = R1 + R2 (since they are combined in series)
= 12 + 20
= 32 ohms
Thus, the total resistance of the combination is 32 ohms.