A mixture of hellium and oxygen gas is expended from a volume of $67\mathrm{.}0L,$ to a velume of $71\mathrm{.}0L,$ while the pressure is heid constant at $74\mathrm{.}0$ atm. Calalate the work done on the gas mixture. Be sure your answer has the correct signi $($pasitive or negative$)$ and the correct number of signinent digts.