In a further experiment, a spring is at the bottom of a 30 degree rough incline. A 5.0 kg mass is released from rest at the top of the incline and slides down the incline and it is momentarily stopped by the spring (k=7840 N/m). The total distance, including the distance that the spring is compressed, that is travelled by the mass is 40 cm. The spring is compressed 3.0 cm when the mass is momentarily stopped. Calculate the coefficent of kinetic friction between the mass and the surface of the incline.