An air$-$filled parallel$-$plate capacitor is constructed with a plate area of $0\mathrm{.}49$ m$2$and a plate separation of $0\mathrm{.}25$ mm$.$ It is then charged to a potential difference of $18$ V$?($$0=8\mathrm{.}851012$ C$2/$N $$ m$2)$

$($a$)$ How much charge is stored on each of its plates?

$($b$)$ How much energy is stored in it$?$