Let $f(x,y,z)=x^4{y}^2{z}^4$ and $x=s^3{t}^3,y=s{t}^3,$ and $z=s{t}^3.$

$($a$)$ Calculate the primary derivatives

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

$\frac{\text{d}\text{e}\text{l}\text{f}}{\text{d}\text{e}\text{l}\text{y}}=$

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

$$

$$

$($b$)$ Calculate

$\frac{\text{d}\text{e}\text{l}\text{x}}{\text{d}\text{e}\text{l}\text{s}}=3s^2{r}^3$

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

$\frac{\text{d}\text{e}\text{l}\text{t}}{\text{d}\text{e}\text{l}\text{s}}=r^3$

$($c$)$ Use the Chain Rule to compute

$\frac{}{8t}=$

$$

In $($c$)$ express your answer in terms of the independent variables $t,s$