A motor delivers 500 hp to the steel shaft AB, which is tubular and has an outer diameter of 2 in. and an inner diameter of 1.84 in. Determine the smallest angular velocity at which it can rotate if the allowable shear stress for the material is τallow = 25 ksi.
a) 1500 rpm
b) 2000 rpm
c) 2500 rpm
d) 3000 rpm