The average (arithmetic mean) distance traveled by five airplanes is 1,200 miles. If the average distance traveled by three of the airplanes is 800 miles, then the average distance, in miles, traveled by the other two planes is:
A. 1000
B. 1040
C. 1600
D. 1800
Total for 5 planes: 1200 x 5 = 6000
Total for 3 planes: 800 x 3 = 2400
6000 - 2400 = 3600 left as total for two planes
3600/2 = 1800