Connect $(\frac{\text{d}\text{e}\text{l}\text{P}}{\text{d}\text{e}\text{l}\text{T}}{)}_S$ to $(\frac{\text{d}\text{e}\text{l}\text{H}}{\text{d}\text{e}\text{l}\text{V}}{)}_P$ and $T.$

Hints: $1)$ select an appropriate Maxwell relationship for the $(\frac{\text{d}\text{e}\text{l}\text{P}}{\text{d}\text{e}\text{l}\text{T}}{)}_S$ expression $-$ be mindful of the

constraint; $2)$ identify another useful equation $($in the notes$)$ to be able to connect $dH,$ and differentiate it

appropriately.