A force, whose direction is upwards parallel to a line of greatest slope of a plane inclined at 35° to the horizontal, acts on a box of mass 15 kg which is at rest on the plane. The normal component of the contact force on the box has magnitude \(R\) newtons (see Fig. 1).

(i) Show that \(R = 123\), correct to 3 significant figures.

When the force parallel to the plane acting on the box has magnitude \(X\) newtons the box is about to move down the plane, and when this force has magnitude \(5X\) newtons the box is about to move up the plane (see Fig. 2).

(ii) Find the value of \(X\) and the coefficient of friction between the box and the plane.