Harry ran for 5 miles. He started at 10:30 and finished at 11:20. What was Harry's average speed in miles per hour?

Answer 1

The answer I got was 6.25 mph.

d=r*t
5=r*.80
5/.80=6.25

but the answers to choose from are:
3
4
5
6

Answer 2

What does r and t stand for