Two identical cylinders C1 and C2, each of radius r and weight P, are tied together by a cord. They support a third cylinder C3 of radius R and weight Q. There is no friction, and the tension in the cord is just sufficient to make the contact force between C1 and C2 zero. Find: a) the tension in the cord, b) the force exerted by the ground on C1, c) the normal force between C1 and C3.