Current I flows through a long thin walled metallic cylinder of radius R with a thin longitudinal slit of width x (x << R) running parallel to the axis of the cylinder. The magnetic induction B produced at any point on the axis of the cylinder is approximately

A

B = zero

B

$$B = \frac{\mu_0 I}{2\pi R}$$

C

$$B = \frac{\mu_0 I x}{2\pi R^2}$$

D

$$B = \frac{\mu_0 I x}{4\pi^2 R^2}$$