A small smooth ring R, of mass 0.6 kg, is threaded on a light inextensible string of length 100 cm. One end of the string is attached to a fixed point A. A small bead B of mass 0.4 kg is attached to the other end of the string, and is threaded on a fixed rough horizontal rod which passes through A. The system is in equilibrium with B at a distance of 80 cm from A (see diagram).

1. Find the tension in the string.
2. Find the frictional and normal components of the contact force acting on B.
3. Given that the equilibrium is limiting, find the coefficient of friction between the bead and the rod.