Tina Is Training for a Biathlon

Multiple Choice

Tina is training for a biathlon. To train for the running portion of the race, she runs 14 miles each day, over the same course. The first 4 miles of the course is on level ground, while the last 10 miles is downhill. She runs 3 miles per hour slower on level ground than she runs downhill. If the complete course takes 1 hour, how fast does she run on the downhill part of the course?

A) 18 mph
B) 12 mph
C) 9 mph
D) 30 mph
E) 15 mph