Choose the correct simplification of the expression (5xy^5)^2(y^3)^4

First bring the outside exponent into the parenthesis. The rule for power to a power is to multiply the powers.
5^2 x^2 y^5^2 y^3^4
25 x^2 y^10 y^12
Then combine the base y's. This rule is keep the base and add the powers.
25 x^2 y^22