If $a^5 +5a^4 +10a^3 +3a^2 -9a-6 = 0$ where $a$ is a real number other than $-1$, what is $(a + 1)^3$?

$ 
\textbf{a)}\ 1
\qquad\textbf{b)}\ 3\sqrt 3
\qquad\textbf{c)}\ 7
\qquad\textbf{d)}\ 8
\qquad\textbf{e)}\ 27
$