The ratio of the number of students in class A, B and C is 7: 9: 5. If 40 students leave B and join A, then the ratio of the number of students in A and B will be 1: 1. Find the total number of students in classes A, B and C.

The ratio of the number of students in class A, B and C is 7: 9: 5. If

1.	The ratio of the number of students in class A, B and C is 7: 9: 5. If 40 students leave B and join A, then the ratio of the number of students in A and B will be 1: 1. Find the total number of students in classes A, B and C.
A.	844
B.	840
C.	420
D.	162
Answer» C. 420