A piston/cylinder assembly contains $0.5 \mathrm{kg}$ of air at $500 \mathrm{kPa}$ and $500 \mathrm{K}$. The air expands in a process such that $P$ is linearly decreasing with volume to a final state of $100 \mathrm{kPa}, 300 \mathrm{K}$. Find the work in the
process.