Simplify the following expression to simplest form using only positive exponents.
(16x^-8y^20)^3/4
(2^4 * x^-8 * y^20)^(3/4)
2^(4 * 3/4) * x^(-8 * 3/4) * y^(20 * 3/4)
2^3 * x^-6 * y^15
8 * y^15 / x^6
(16x^-8y^20)^3/4
2^(4 * 3/4) * x^(-8 * 3/4) * y^(20 * 3/4)
2^3 * x^-6 * y^15
8 * y^15 / x^6