Two rotors \(A\) and \(B\) are connected to the two ends of a shaft of uniform diameter. The mass moment of inertia of rotor \(A\) about the axis of the shaft is four times that of \(B\). If the length of the shafts is \(1 \mathrm{~m}\) and \(C\) is the position of node for torsional vibrations, then what is the length of \(A C\) ?

(a) \(1 / 5 \mathrm{~m}\)

(b) \(4 / 5 \mathrm{~m}\)

(c) \(1 / 25 \mathrm{~m}\)

(d) \(16 / 25 \mathrm{~m}\).