$19.$ An electron is accelerated from rest through a potential difference of $3750$ V$.$ It enters a region where the magnetic field is $4\mathrm{.}0$mT perpendicular to the velocity of the electron. Calculate the radius of the path this electron will follow.

A$)2\mathrm{.}2$cm

B$)4\mathrm{.}2$cm

C$)5\mathrm{.}2$cm

D$)1\mathrm{.}2$cm

E$)3\mathrm{.}2$cm