A solid shaft is transmitting power with stress acting on it as shown in figure below. REBO T 100 MPa, d = 10 mm Shear stress (T) is varying along the radius as 10 MPa/mm. If the shaft can transmit a maximum torque of 50 N-m, the factor of safety according to Trescas theory is (a) 1.80 (b) 3.6 (c) 2 (d) 7.2