Mrs. Calalang drives a distance of 15 km at a speed of km/h to go from her house to school. To go back from school to her house, she uses the same road and drives at a speed of 3 km/h slower due to heavy traffic.
a. Express Mrs. Calalang's average speed for her round-trip.
b. Determine Mrs. Calalang's average speed if her speed in going from her house to school is 65 km/h.
