ONLY D AND E PLEASE!!!!!

For the following functions find all of the critical points and then classify them using the second derivative test.

$($a$)f(x,y)=x^3-2xy8y^3.$

$($b$)g(x,y)=3x^2{y}^3-6xy.$

$($c$)h(x,y)=x^{2}y{y}^3-x^2-3y^2.$

$($d$)$

$F(x,y)=e^{(\frac{x^3}{3}-x-y^2)}$

$($e$)$

$G(x,y)=8xy\frac{16}{x}\frac{32}{y}$