Suppose an ideal monatomic gas has a pressure of 1.000 atm at $273.15 \mathrm{~K}$ and is then cooled at constant pressure until its volume is reduced by $47.53 \% .$ The amount of work done by the gas is $-7.540 \cdot 10^{1} \mathrm{~J}$. How many moles of gas are there?