ratio of power transmitted by shaft A to shaft B

Question

Two shafts A and B are made of the same material. The diameter of shaft B is twice that of shaft A. the ratio of power which can be transmitted by shaft A to that of shaft B is (If maximum shear stress remains the same)

(a)                            (b)

(c)                             (d)

Answer 1

Given two shafts of same material, where maximum shear stress of the shafts is constant