Q$\mathrm{.}3$ Consider a piston$-$cylinder assembly that contains $1$ mole of ideal gas A$.$ The system is well insulated. Its initial volume is $10$ L$,$ and its initial pressure is $2$ bar. The gas is allowed to expand against a constant external pressure of $1$ bar until it reaches mechanical equilibrium. a$)$ What is the final temperature of the system? b$)$ How much work was obtained? For gas A: Cv $=2\mathrm{.}5$R$.$