A plane flies over city A and reaches city B in 12 minutes, which is 120 miles away from it. Find the speed of the plane in miles per hour assuming the plane flew at a constant speed.

A. 300 mi./hr.
B. 450 mi./hr.
C. 600 mi./hr.
D. 680 mi./hr.

ANSWER TO MY OWN QUESTION:    C. 600 mi./hr.