The spring$-$loaded piston$-$cylinder device shown in Fig. $1$ is filled with $0\mathrm{.}5$ kg of water vapor that is initially at $4$ MPa and $400C.$ Initially, the spring exerts no force against the piston. The spring constant in the spring force relation $F=kx$ is $k=0\mathrm{.}9k\frac{N}{m}$ and the piston diameter is $D=20cm.$ The water now undergoes a process until its volume is one$-$half of the original volume. Calculate the final temperature and the specific enthalpy of the water.

Fig. $1$ The schematic of question $3.$