Can someone please help me?? And tell me how you got your answer?? I keep getting -6a^2b^2

You're getting the answer that any regular person who didn't see the exponents floating way above the expressions there would get.
I think the problem is actually:
[tex] 3 a^2b \times -2 ab^3 = -6 a^3 b^4 [/tex]
Choice D