A woman drives a car from one city to another with different constant speeds along the trip. She drives at a speed of 85.0 km/h for 20.0 min, 55.0 km/h for 15.0 min, makes a stop for 35.0 min, then continues at 45.0 km/h for 30.0 min, at which point she reaches her destination.
(1) What is the average speed for the entire trip (in units of km/h)?
a) 62.5 km/h
b) 67.5 km/h
c) 72.5 km/h
d) 77.5 km/h
