Answer:
I belive the answer would be the first one. 2^28 x 3^20 x 9^4
Explanation:
This is becasue you need to multiply the power on the outside of the parenthesis, (4). 7 times itself 4 times is 28, 5 times itself 4 times is 20, and then use the 4 for the 9. Hope this helps!