3.23: Show a linear relation, then find $a$, $b$, $c$

The polynomial $p$ is such that $p(x) = ax^{3} + bx^{2} - 19x + c$, where $a$, $b$ and $c$ are integers. It is given that $x + 2$ is a factor of $p(x)$. When $p(x)$ is divided by $x + 1$ the remainder is $20$.