1.13: Factor and remainder on a cubic

It is given that $p(x) = 2x^{3} + ax^{2} + 4x + b$, where $a$ and $b$ are constants. It is given also that $2x + 1$ is a factor of $p(x)$ and that when $p(x)$ is divided by $x - 1$ there is a remainder of $-12$.