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` becomes equal in strength. How many students are there in section `A` and `B` ? (a) 80, 40 (b) 90, 40 (c) 45, 15 (d) 50, 30