Two parallel conducting plates are separated by $10\mathrm{.}0$ cm$,$ and one of them is taken to be at zero volts.

$($a$)$

What is the electric field strength $($in kV$/$m$)$ between them, if the potential $8\mathrm{.}00$ cm from the zero volt plate $($and $2\mathrm{.}00$ cm from the other$)$ is $450$ V$?$

$5\mathrm{.}625$ kV$/$m

$($b$)$

What is the voltage between the plates?