AMC 8 2016 Problem 4

When Cheenu was a boy he could run $15$ miles in $3$ hours and $30$ minutes. As an old man he can now walk $10$ miles in $4$ hours. How many minutes longer does it take for him to walk a mile now compared to when he was a boy? $\textbf{(A) }6 \textbf{(B) }10 \textbf{(C) }15 \textbf{(D) }18 \textbf{(E) }30$