4. As shown in the figure, on grid paper with unit squares, the three-view of a geometric solid obtained by cutting off part of a cylinder with a plane is shown. The volume of this geometric solid is
A. $90 \pi$
B. $63 \pi$
C. $42 \pi$
D. $36 \pi$ [Figure] [Figure]
5. Let $x , y$ satisfy the constraints $\left\{ \begin{array} { l } 2 x + 3 y - 3 \leqslant 0 , \\ 2 x - 3 y + 3 \geqslant 0 , \\ y + 3 \geqslant 0 , \end{array} \right.$ then the minimum value of $z = 2 x + y$ is
A. $-3$
B. $- 9$
C. $1$
D. $9$