An electron moves through a uniform magnetic field → B = B _ 0 ^ i...

Force acting on a charged particle under the magnetic field is given by, $\overset{\to}{F} = q\left(\overset{\to}{v} \times \overset{\to}{B}\right)$.

$⇒ 5e\overset{⏜}{k} = e\left(3\overset{⏜}{i} + 5\overset{⏜}{j}\right) \times \left({B}_{0}\overset{⏜}{i} + 2{B}_{0}\overset{⏜}{j}\right)$

$⇒ 5e\overset{⏜}{k} = e\left(6{B}_{0}\overset{⏜}{k} - 5{B}_{0}\overset{⏜}{k}\right)$

$⇒ {B}_{0} = 5T$