1970 AHSME Problem 28

In triangle ABC, the median from vertex A is perpendicular to the median from vertex B. If the lengths of sides AC and BC are 6 and 7 respectively, then the length of side AB is

\textbf{(A) }\sqrt{17}\qquad \textbf{(B) }4\qquad \textbf{(C) }4\dfrac{1}{2}\qquad \textbf{(D) }2\sqrt{5}\qquad \textbf{(E) }4\frac{1}{4}

Full credit goes to MAA for authoring these problems. These problems were taken on the AOPS website.