Two pulleys of diameters d1 and d2 and at distance x apart are connected by means of an open belt drive. The length of the belt is

(a) π /2 (d1 + d2) 2x + (d1 + d2)^2/4x

(b) π /2 (d1 – d2) 2x + (d1 – d2)^2/4x

(c) π /2 (d1 + d2) 2x + (d1 – d2)^2/4x

(d) π /2 (d1 – d2) 2x + (d1 + d2)^2/4x

I got this question in unit test.

Query is from Belt, Rope and Chain Drives topic in portion Belt, Rope and Chain Drives of Machine Kinematics