The refracting angle of a prism is A and the refractive index of the material of the prism is $\cot (A/2)$. The angle of minimum deviation of the prism is :

Question

$$\begin {array} {1 1} (a)\;\pi+2A & \quad (b)\;\pi-2A \\ (c)\;\frac{\pi}{2}+A & \quad (d)\;\frac{\pi}{2}-A \end {array}$$