Donna is a mountain biking enthusiast. One Saturday, she spent the morning biking up an uphill trail at an average speed of 20 kilometers per hour, and then returned by the same route in the afternoon at an average speed of 25 kilometers per hour. If the downhill trip in the afternoon took 3/4 of an hour less than the uphill trek in the morning, how many kilometers did Donna ride each way ？（）
A. 50
B. 55
C. 65
D. 70
E. 75