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

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