Catherine simplifies 6^a x 6^3/ 6^b to 6^(a-3+b)

Justin simplifies the same expression but gets a different answer, 6^(a+3)-b
Part A: Who is correct?
1. Catherine is correct.
2. Both of them have equivalent expressions.
3. Justin is correct.
4. Neither Catherine or Justin is correct.

1. Catherine is correct.