Determine the couple moment M that must be applied to member DC for equilibrium of the quick-return

Question:

Determine the couple moment M that must be applied to member DC for equilibrium of the quick-return mechanism. Express the result in terms of the angles ? and ?, dimension L, and the applied force P, which should be changed in the figure and instead directed horizontally to the right. The block at C is confined to slide within the slot of member AB.