I've been working on this problem and can't figure out how to get to the right answer.

The problem:

(5x-2)^2(2-x^4)^4

I got:

2(5x-2)(2-x^4)^3(20+16x^3-50x^4)

But the correct answer, according to the online set, is:

2(5x-2)(2-x^4)^3(10+16x^3-45x^4)

I sometimes get tripped up on factoring out, but I can't see where I went wrong. My answer seems right. I don't know how to get to the correct answer.