AMC 8 1995 Problem 25

Buses from Dallas to Houston leave every hour on the hour. Buses from Houston to Dallas leave every hour on the half hour. The trip from one city to the other takes $5$ hours. Assuming the buses travel on the same highway, how many Dallas-bound buses does a Houston-bound bus pass in the highway (not in the station)? $\text{(A)}\ 5 \text{(B)}\ 6 \text{(C)}\ 9 \text{(D)}\ 10 \text{(E)}\ 11$