1985 AJHSME Problem 13

If you walk for 45 minutes at a rate of 4 \text{ mph} and then run for 30 minutes at a rate of 10\text{ mph,} how many miles will you have gone at the end of one hour and 15 minutes?

\textbf{(A)}\ 3.5\text{ miles} \qquad \textbf{(B)}\ 8\text{ miles} \qquad \textbf{(C)}\ 9\text{ miles} \qquad \textbf{(D)}\ 25\frac{1}{3}\text{ miles} \qquad \textbf{(E)}\ 480\text{ miles}

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