Chapter 14.R, Problem 37E

Suppose $z=f\left(x,y\right)$, where $x=g\left(s,t\right)$, $y=h\left(s,t\right)$, $g\left(1,2\right)=3$, $g_s\left(1,2\right)=-1$, $g_t\left(1,2\right)=4$, $h\left(1,2\right)=6$, $h_s\left(1,2\right)=-5$, $h_t\left(1,2\right)=10$, $f_x\left(3,6\right)=7$, and $f_y\left(3,6\right)=8$. Find $\partial z/\partial s$ and $\partial z/\partial t$ when $s=1$ and $t=2$.