AHSME 1950 Problem 35

In triangle $ABC$, $AC=24$ inches, $BC=10$ inches, $AB=26$ inches. The radius of the inscribed circle is: $\textbf{(A)}\ 26\text{ in} \textbf{(B)}\ 4\text{ in} \textbf{(C)}\ 13\text{ in} \textbf{(D)}\ 8\text{ in} \textbf{(E)}\ \text{None of these}$