A stadium charges $75 for each seat in section A, $50 for each seat in section B, and $40 for section C. There are three times as many seats in section B as in section A. The revenue from selling odd 20,000 seats is 897,500. Write a system to represent the situation.

A. b=3×c
a+b+c=20,000
75a+50b+40c=897,500

B. b=3×a
a+b+c=20,000
75a+50b+40c=897,500

C. a=3×b
a+b+c=20,000
40a+50b+75c=897,500

D. a=3×b
a+b+c=20,000
75a+50b+40c=897,500​