Amber and Austin were driving the same route from college to their home town. Amber left 2 hrs before Austin. Amber drove at an average speed of 55 mph, and Austin averaged 75 mph per hour. After how many hours did Austin catch up with Amber?
A. 10 h
B. 7.5 h
C. 5.5 h
D. 2 h
Ps. answer B. 7.5 h is wrong. I just took the test and doing a redo.