AMC8 1992 Problem 18

On a trip, a car traveled 80 miles in an hour and a half, then was stopped in traffic for 30 minutes, then traveled 100 miles during the next 2 hours. What was the car’s average speed in miles per hour for the 4 -hour trip?

Answer Choices
A. 45
B. 50
C. 60
D. 75
E. 90