The graph shows the curve

\(y=a\cos bx+c,\)

for \(0\leq x\leq2.8\), where \(a\), \(b\) and \(c\) are constants and \(x\) is in radians. The curve meets the \(y\)-axis at \((0,3)\) and the \(x\)-axis at the point \(P\) and point \(R\left(\frac{5\pi}{6},0\right)\).

The curve has a minimum at point \(Q\). The period of \(a\cos bx+c\) is \(\pi\) radians.

(a) Find the value of each of \(a\), \(b\) and \(c\).

(b) Find the coordinates of \(P\).

(c) Find the coordinates of \(Q\).