A $400-\mathrm{L}$ tank, $A$ (see Fig. $\mathrm{P} 4.33$ ), contains argon gas at $250 \mathrm{kPa}$ and $30^{\circ} \mathrm{C}$. Cylinder $B$, having a frictionless piston of such mass that a pressure of 150 kPa will float it, is initially empty. The valve is opened and argon flows into $B$ and eventually reaches a uniform state of $150 \mathrm{kPa}$ and $30^{\circ} \mathrm{C}$ throughout. What is the work done by the argon?