1997 Cayley Problem 12

Three small rectangles, of the same depth, are cut from a rectangular sheet of metal. The area of the remaining piece is 990. What is the depth of each cut?

\textbf{(A)}\ 8\quad \textbf{(B)}\ 7\quad \textbf{(C)}\ 6\quad \textbf{(D)}\ 5\quad \textbf{(E)}\ 4

If there are no answer choices shown, enter a numerical answer.

Full credit to this problem is given to the CEMC, you may view all Cayley contests here.