A2. What is the exact volume of the solid obtained by rotating a rectangle with sides $a=2$ $cm$ and $b=3 \, cm$ about the perpendicular bisector of the shorter side?
(A) $2 \pi \, cm^{3}$
(B) $4 \pi \, cm^{3}$
(C) $12 \pi \, cm^{3}$
(D) $\pi \, cm^{3}$
(E) $3 \pi \, cm^{3}$
A2. If we rotate a rectangle with sides $a=2 \mathrm{~cm}$ and $b=3 \mathrm{~cm}$ around the axis of symmetry of the shorter side, we get a solid of revolution in the form of a cylinder with radius $r=1 \mathrm{~cm}$ and height $v=3 \mathrm{~cm}$. The volume of the cylinder can be calculated using the formula $V=\pi r^{2} v=3 \pi \mathrm{cm}^{3}$. The correct answer is $E$.