A square has sides of 12 units. Squares of $x+1$ by $x+1$ units are cut out of each corner, and then the sides are folded up to create an open box. Express the volume of the box as a polynomial function in terms of $x$. Volume of the box is calculated by multiplying height, length, and width.
$V(x) = 4x^3 - 48x^2 + 144x$
$V(x) = 4x^3 + 48x^2 + 144x + 50$
$V(x) = 4x^3 - 36x^2 + 60x + 100$
$V(x) = 4x^3 - 40x^2 + 100x$
