A 2.40 kg block of wood is resting on a horizontal surface. It is attached to a massless string which passes over a pulley. The other end of the string is attached to a 3.60 kg block suspended in the air. When released the 3.60 kg block begins to descend with an acceleration of 3.92m/s2. What is the coefficient of kinetic friction between the 2.40 kg block and the table?