The bar shown in the figure is tapered linearly from end A to end B and has a solid circular cross section. The diameter at the smaller end of the bar is d A = 25 mm and the length is L = 300 mm. The...

The bar shown in the figure is tapered linearly from end A to end B and has a solid circular cross section. The diameter at the smaller end of the bar is d_A
= 25 mm and the length is L = 300 mm. The bar is made of steel with shear modulus of elasticity G = 82 GPa.

If the torque T = 180 N.m and the allowable angle of twist is 0.38, what is the minimum allowable diameter dB at the larger end of the bar?