Simplify with Positive Exponents:

(2x^{-2}b^{4})^{-2}

I know thecorrectanswer is

but for some reason I keep getting a totally different answer. Which is:

I am following the rules of the exponents but maybe I am making a simple mistake somewhere? Can someone explain to me how to get the correct answer? Thank you!

Edit: I figured out what I was doing wrong!

(2x^{-2}b^{4})^{-2 }-4x^{4}b^{-8}

I didn't distributed the -2 properly.