Sam is training for the marathon. He drove 12 miles from his home to the Grey Hills Park and then ran 6 miles to Red Rock, retraced his path back for 2 miles, and then ran 3 miles to Rock Creek. If he is then n miles from home, what is the range of possible values for n ？（）

A. 1≤n≤23

B. 3≤n≤21

C. 5≤n≤9

D. 6≤n≤18

E. 9≤n≤15

货币学派和供给学派的主张有何不同？