Fourier Series; odd and even half-range expansion

Question

I have some standard Fourier series questions which I cannot solve. My fourier series is defined like this:

$$s(x)=\frac{a_0}{2} + \sum_{n=1}^{\infty} (a_n \cos (nx) + b_n \sin (nx))$$

For $f(t) = \pi - t$ , where $0<t<\pi$,

q1) find the $b_n$ coefficient of the odd expansion,

q2) find the $a_0$ and $a_n$ coefficients of the even expansion.

1. my attempt; which is apparently wrong
2. I got $a_n=\frac{2}{\pi}\frac{1-\cos(\pi\,n)}{n^2}\ ,\quad a_0=\pi$. Don't know whether it's wrong or not.