Turning effects of forces — practice question

A rigid plank is used to form a ramp linking two horizontal levels of ground, as illustrated in Fig. 4.1. At the lower end, point A of the plank rests on the lower level of the ground. At point B, a force acts on the plank at right angles to it. A rope from point D on the plank to the ground keeps the plank in equilibrium. The plank’s weight may be treated as acting through its centre of gravity C. The rope is perpendicular to the plank and has tension $T$. The plank makes an angle of $38^{\circ}$ to the vertical. The forces and the distances measured along the plank for points A, B, C and D are shown in Fig. 4.1.