AMC 12 2006b Problem 2

For real numbers $x$ and $y$, define $x\spadesuit y = (x + y)(x - y)$. What is $3\spadesuit(4\spadesuit 5)$?

$\text {(A) } - 72 \text {(B) } - 27 \text {(C) } - 24 \text {(D) } 24 \text {(E) } 72$