2001 Gauss 8 Problem 18

Two squares are positioned, as shown. The smaller square has side length 1 and the larger square has side length 7. The length of AB is

\textbf{(A)}\ 14\quad \textbf{(B)}\ \sqrt{113}\quad \textbf{(C)}\ 10\quad \textbf{(D)}\ \sqrt{85}\quad \textbf{(E)}\ \sqrt{72}

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 Gauss contests here.