Let \(f:[-2a,2a]\to\mathbb{R}\) be a thrice differentiable function and define
\[
g(x)=f(a+x)+f(a-x).
\]
If \(m\) is the minimum number of roots of \(g'(x)=0\) in the interval \((-a,a)\) and
\(n\) is the minimum number of roots of \(g''(x)=0\) in the interval \((-a,a)\),
then \(m+n\) is equal to: