A current `I` flows through a long straight conductor which is bent into a circular loop of radius R in the middle as shown in the figure.
The magnitude of the net magnetic field at point `O` will be
Options:
(a) zero
(b) `(mu_0I)/(2R)(1+pi)`
(c) `(mu_0)/(4piR)`
(d) `(mu_0l)/(2R)(1-1/pi)`