Example: Plate clutch having a single driving plate with two contact surfaces on each side is required to transmit $110$ kW at $1250$ r$.$p$.$m$.$ The outer diameter of the contact surfaces is to be $300$ mm $.$ The coefficient of friction is $0\mathrm{.}4.$ a$.$ Assuming a uniform pressure of $0\mathrm{.}17\frac{N}{m}m2$; determine the inner diameter of the friction surfaces.

$T=2pf(\frac{R_o^3-R_i^3}{3})$