Find the derivative of the function f(x) = (2x³ - 7x² - 9)⁵.
a) 10x²(2x³ - 7x² - 9)⁴
b) 5(2x³ - 7x² - 9)⁴
c) 5x(2x³ - 7x² - 9)⁴
d) 10x(2x³ - 7x² - 9)⁴