A uniform magnetic field exist in a region which forms an equilateral triangle of side a. The magnetic field is perpendicular to the plane of the triangle . A charged q enters into this magnetic field perpendicular to a side with speed v. The charge enters from midpoint and leaves the field from midpoint of other side. Magnetic induction in the triangles is

Options

A. `(mv)/(qa)`
B. `(2mv)/(qa)`
C. `(mv)/(2qa)`
D. `(mv)/(4qa)`