Calculate the total angle of twist for a stepped shaft which is subjected to the torque (T) as shown in the figure below.

A

$$\frac{Tl}{\pi Gd^4}$$

B

$$\frac{66Tl}{\pi Gd^4}$$

C

$$\frac{Tl}{66 Gd^4}$$

D

$$\frac{36Tl}{\pi Gd^4}$$