One end of a heavy uniform rod AB can slide along rough horizontal guiding surface CD with the help — AITS & Test Series Chemistry Question

Question

One end of a heavy uniform rod AB can slide along rough horizontal guiding surface CD with the help of massless ring as shown in the figure. The dimension of ring is negligible. BE is the ideal string. If ∠EBA is right angle and α is the angle between rod AB and horizontal when the rod is on the verge of sliding. Find the coefficient of friction between ring and horizontal guiding surface CD.