The winning car in a race traveled the race distance of 450 miles at an average speed of 120 miles per hour (mph). The car finished the race in 3 hours and 45 minutes. The last car to cross the finish line took 4 hours and 30 minutes. What was its average speed?
a. 104.7 mph
b. 100 mph
c. 112.5 mph
d. 90 mph