A non-uniform plank \(AB\) of length \(6.0\text{ m}\) and weight \(180\text{ N}\) rests horizontally on two supports: one at end \(A\), and one at a point \(C\) located \(5.0\text{ m}\) from \(A\). The plank's centre of gravity is \(2.5\text{ m}\) from \(A\). A load of weight \(150\text{ N}\) is placed at end \(B\), as shown.


What is the magnitude of the reaction force at support \(C\)?