The height \(h\) of Porter governor with equal arms pivoted at equal distance from axis of rotation is expressed as (where \(m=\) mass of balls of the governor, \(M=\) mass of sleeve of the governor and \(N=\mathrm{rpm})\)

(a) \(h=91.2\left[\frac{m+M}{m}\right] \frac{g}{N^{2}}\)

(b) \(h=91.2\left[\frac{m g-M g}{m g}\right] \frac{g}{N^{2}}\)

(c) \(h=91.2\left[\frac{m}{m M}\right] \frac{g}{N^{2}}\)

(d) \(h=91.2\left[\frac{M}{m}\right] \frac{g}{N^{2}}\)