Van der waals gas

[conv]

Homework Statement

I have put a picture of the task below. Anyone who can help solving it?

Relevant Equations

(P + an^2/V^2)(V−nb) = nRT

 

[Ssnow]

Hi, you have all terms in the equation but not $P$ the pressure, you can start to find $P$ ... after you can reasoning on the force on the piston considering that the gas is in equilibrium...
Ssnow