Which of the following is equivalent to A^t·B^6t

1. (AB)^6·(t^2)
2. (A+B)^7t
3. (AB)^6t
4. None of the above

A^t·B^6t = (AB^6)^t
Answer: 4. None of the above

the answer might be 1st option.
(AB^6)^t except it cant go further i think so.
lets see 1st option (AB)^6·(t^2)= (AB)^(6*t*t)= (A^t.B^6t.

Agree with the first answer above.