Let p(x) be the taylor polynomial of degree n of the function

f(x) = log(1-x), about a = 0. How large should n be chosen to have

|f(x) - p(x)| <= 10^-4 ?

So I know how to go about this, but for Rn, what is f^(n+1) ?

Which derivative do I use? How do I know which to do?

Can someone give me the approximate n I'm looking for and the formula you used to get there, with details?

Thanks