For the function $F=F(x,y)$, we can plot the function in 3-dimensions by choosing $z=F(x,y)$ which represents a surface. I require to plot the following projections:
1. The projection of the surface $F(x,y)$ on the $xz$-plane and on the $yz$-plane.
2. The projection of the extremas of $F(x,y)$ on the $xz$-plane and on the $yz$-plane.