In the figure a charged particle $($either an electron or a proton$)$ is moving rightward between two parallel charged plates separated by

distance $d=1\mathrm{.}10mm.$ The plate potentials are $V_1=-70\mathrm{.}0V$ and $V_2=-49\mathrm{.}0V.$ The particle is slowing from an initial speed of $85\mathrm{.}0k\frac{m}{s}$

at the left plate. $($a$)$ Is the particle an electron or a proton? $($b$)$ What is its speed just as it reaches plate $2?$