Use the chain rule $to$ find $\frac{\text{d}\text{e}\text{l}\text{z}}{\text{d}\text{e}\text{l}\text{s}}$ and $\frac{\text{d}\text{e}\text{l}\text{z}}{\text{d}\text{e}\text{l}\text{t}}.$

$,z=e^{x+7y},x=\frac{s}{t},y=\frac{t}{s}$

$\frac{\text{d}\text{e}\text{l}\text{z}}{\text{d}\text{e}\text{l}\text{s}}=\frac{e^{(\frac{s}{t})}}{t}-\frac{7t}{s^2}x$

$\frac{\text{d}\text{e}\text{l}\text{z}}{\text{d}\text{e}\text{l}\text{t}}=$