Prove $($a$)(\frac{\text{d}\text{e}\text{l}\text{H}}{\text{d}\text{e}\text{l}\text{P}}{)}_T=V(1-T),$ where is the isobaric thermal coefficient of expansion and $V$ is the volume. $($b$)(\frac{\text{d}\text{e}\text{l}\text{T}}{\text{d}\text{e}\text{l}\text{P}}{)}_H=$