Suppose two rotors with inertias \(I_{1}\) and \(I_{2}\) on shafts of lengths \(l_{1}\) and \(l_{2}\) respectively, are connected by gears such that the speed of the \(I_{2}\) rotor is always \(G\) times that of the \(I_{1}\) rotor. This system may, for vibration analysis, be treated as being on one shaft (integral with \(l_{1}\) ) if

(a) \(I_{1}\) is changed to \(G^{2} I_{1}\)

(b) \(I_{2}\) is changed to \(G^{2} I_{2}\)

(c) \(I_{1}\) is changed to \(I_{1} / G^{2}\)

(d) \(I_{2}\) is changed to \(I_{2} / G^{2}\).