In a class there are two sections A and B. If 10 students of section B shift over to section A, the strength of A becomes three times the strength of B. But if 10 students shift over from A to B, both A and B become equal in strength. How many students are there in sections A and B?

• A.50 and 30
• B.45 and 15
• C.90 and 40
• D.80 and 40