An ideal monatomic gas is confined within a cylinder by a spring...

An ideal monatomic gas is confined within a cylinder by a spring loaded piston of cross-sectional area $4 \times 10^{-3} \mathrm{~m}^2$. Initially the gas is at 400 K and occupies a volume $2 \times 10^{-3} \mathrm{~m}^3$ and the spring is in its relaxed position. The gas is heated by an electric heater for some time. During this time the gas expands and the piston moves out by a distance 0.1 m . The spring connected to the rigid wall is massless and frictionless. The force constant of the spring is $2000 \mathrm{Nm}^{-1}$ and atmospheric pressure is $10^5 \mathrm{Nm}^{-2}$ then