The number a is 24, the least common multiple of a and B is 168, the greatest common factor is four, what is the number B?

The number a is 24, the least common multiple of a and B is 168, the greatest common factor is four, what is the number B?

168÷4=42 42=6×7
So 4 × 6 = 24 (a)
4 × 7 = 28 (b)