A heat engine does work by using a gas at an initial pressure of $1000$ Pa and volume $\mathrm{.}1$m $3.$ Step$-$by$-$step, it then increases the pressure to $10,000$ Pa $($at constant volume$),$ increases the volume to $\mathrm{.}15$m$3($at constant pressure$),$ decreases the pressure back to $1,000$ Pa $($at constant volume$)$ and returns the volume back to $\mathrm{.}1$m$3($at constant pressure$).$

$5)$How much work is done by the gas during the first step?