An electron moves through a uniform magnetic field $\overrightarrow{B}=(B_0\widehat{i}+2B_0\widehat{j})T$ . At a particular instant of time, the velocity of electron is  $\overrightarrow{u}=(3\widehat{i}+5\widehat{j})m/s$ If the magnetic force acting on electron is $\overrightarrow{F}=\left(5e\widehat{k}\right)N,$  where e is the charge of electron, then the value of  $B_0$ is