A shaft, supported on two bearings at its ends, carries two flywheels ' \(L\) ' apart. Mass moment of inertia of the two flywheels are \(I_{a}\) and \(I_{b}\), I being the polar moment of inertia of cross-sectional area of the shaft. Distance \(l_{a}\) of the mode of torsional vibration of the shaft from the flywheel \(I_{a}\) is given by

(a) \(l_{a}=\frac{L I_{b}}{I_{a}+I_{b}}\)

(b) \(l_{a}=\frac{L I_{a}}{I_{a}+I_{b}}\)

(c) \(l_{a}=\frac{L I_{b}}{I_{a}+I_{b}-I}\)

(d) \(l_{a}=\frac{L I_{a}}{I_{a}+I_{b}-I}\)