The magnetic field at point P in the hollow cylindrical wire carrying a current i shown in the figure at a distance r from axis `(a lt r lt b)` is given by (Taking current density to be uniform across its cross-section)
A. `(mu_(0)i(r^(2) - a^(2)))/(2pi (b^(2) - a^(2))r)`
B. `(mu_(0)ir)/(2pi (b^(2) - a^(2)))`
C. `(mu_(0)iab)/(2pi(b^(2) -a^(2))r)`
D. zero
