A stepped shaft ABCD consisting of solid circular segments is subjected to three torques, as shown in the figure. The torques have magnitudes 12.0 k-in., 9.0 k-in., and 9.0 k-in. The length of each segment is 24 in. and the diameters of the segments are 3.0 in., 2.5 in., and 2.0 in. The material is steel with shear modulus of elasticity G = 11.6 x 103 ksi. Calculate the angle of twist (in degrees) at end D. 3.0 in. A 24 in. 12.0 k-in. BI 9.0 k-in. 9.0 k-in. 2.5 in. | 2.0 in. C ↑ D -24 in.- 24 in.