Two wires AO and OC carry equal currents i as shown in Fig. One end of both the wires extends to infinity. Angle AOC is `alpha`. The magnitude of magnetic field is point P on the bisector of these two wires at a distance r from point O is
A. `(mu_(0))/(2pir) i/r cot((alpha)/2)`
B. `(mu_(0))/(4pir) i/r cot((alpha)/2)`
C. `(mu_(0))/(2pi)(i)/(r )((1+"cos"(alpha)/(2)))/("sin"((alpha)/(2)))`
D. `(mu_(0))/(4pi) (i/r)((alpha)/2)`