The number of students in classes A and B are 60 and 70, respectively. The average score in mathematics of students in B is 57 and that of all students in A and B is 63. What is the average score of students in A?

The number of students in classes A and B are 60 and 70, respectively.

1.	The number of students in classes A and B are 60 and 70, respectively. The average score in mathematics of students in B is 57 and that of all students in A and B is 63. What is the average score of students in A?
A.	69
B.	70
C.	68
D.	71
Answer» C. 68