$[5]$ An electron with mass $m_e=9\mathrm{.}11{10}^{-31}kg$ revolving around a single proton with mass $m_p=1\mathrm{.}67{10}^{-27}kg.$ The proton is nearly $2000$ times as massive as the electron, so we'll assume that the proton doesn't move. The electron moves with speed $v_e$ in a circular orbit with Bohr radius $r_B=0\mathrm{.}529{10}^{-10}m($see Figure$).$ The attractive centripetal force $($electromagnetic force$)$ between the electron and the proton is $F=8\mathrm{.}24{10}^{-8}N.($a$)$ Calculate the speed of the electron $v_e.($b$)$ Calculate the angular momentum $L$ of the electron. Unit of $L$ is $kg\frac{m^2}{s}$ or $Js.$