Sarah ran a 24 mile race. She ran 6 miles in 1 hours, 6 miles in 1.2 hours, 6 miles in 1.5 hours, 6 miles in 1.6 hours. how long did it take her to finish the race?
a) 1.8 hours
b) 2.0 hours
c) 2.2 hours
d) 2.4 hours