Derive a formula for the volume of the wedge in terms of the constants $a$, $b$, $c$.
Seeing a similar triangle, I see that $\frac{x}{y}=\frac{c}{b}$, $y$ being the distance from the $a$ line to the edge. And now $y=\frac{bx}{c}$
The area for the cross section is now $A=\frac{b}{2c}x^2$. I integrate:
$\frac{b}{2c} \int_{0}^{a}x^2dx=\frac{ba^2}{6c}$