A man traveled a total distance of 1800 km. He traveled one-third of the whole trip by plane and the distance traveled by train is two-thirds of the distance traveled by bus. If he traveled by train, plane and bus, how many kilometers did he travel by bus?	Choose the correct choice from the following choices:
A) 660
B) 680
C) 720
D) 760
E) 800

Rationale: "total distance traveled = 1800 km . distance traveled by plane = 600 km . distance traveled by bus = x distance traveled by train = 2 x / 3 x + 2 x / 3 + 600 = 1800 5 x / 3 = 1200 x = 720 km the answer is c ."
Answer: C