AMC 10 2014b Problem 3

Randy drove the first third of his trip on a gravel road, the next $20$ miles on pavement, and the remaining one-fifth on a dirt road. In miles how long was Randy's trip? $\textbf {(A) } 30 \textbf {(B) } \frac{400}{11} \textbf {(C) } \frac{75}{2} \textbf {(D) } 40 \textbf {(E) } \frac{300}{7}$