Let \(f\) be the function defined by \(f(x) = x \cos x - \sin x\). What is the absolute maximum value of \(f\) on the interval \([- \frac{\pi}{2}, 2\pi]\)
a) \(\frac{5\pi}{2}\)
b) \(2\pi\)
c) \(-1\)
d) \(\frac{\pi}{2}\)