Answer
The solid is a part of the 1st octant between the square in the plane $z=0$
and $z=4-x-2y.$
Work Step by Step
The graph of $f(x, y)=4-x-2y $ is a plane,
$0\leq x\leq 1$ and $0\leq y\leq 1,$
and $z=f(x,y)$ is least when $x=1, y=1$, so the solid is the first octant.
The solid is part of the 1st octant between the planes $z$=0 and $z=4-x-2y.$
