An electron moves through a uniform magnetic field given by B $=$ Bx$+(3\mathrm{.}0$ Bx$)$j$.$ At a particular instant, the electron has velocity $=(2\mathrm{.}0$i $+4\mathrm{.}0$ j$)$m$/$s and the magnetic force acting on it is $6\mathrm{.}4$ x $10-19$N k$.$ Find Bx $($a$)-2$ T $($b$)+2$ T $($c$)0\mathrm{.}4$ T $($d$)-0\mathrm{.}4$ T $($e$)-5$ T Ans A