Three cars leave from A to B in equal time intervals. They reach B

Three cars leave from A to B in equal time intervals. They reach B simultaneously and then leave for Point C which is 240 miles away from B. The first car arrives at C an hour after the second car. The third car, having reached C, immediately turns back and heads towards B. The first and the third car meet a point that is 80 miles away from C. What is the difference between the speed of the first and the third car?

A. 60 mph
B. 20 mph
C. 40 mph
D. 80 mph
E. 120 mph