2.36: Area between a cubic and a horizontal line

The diagram shows part of the curve $y = x^{3} + 4x^{2} - 5x + 5$ and the line $y = 5$. The curve and the line intersect at the points $A$, $B$ and $C$. The points $D$ and $E$ are on the $x$-axis and the lines $AE$ and $CD$ are parallel to the $y$-axis.