A 4 kg disk lines in static equilibrium on an incline that makes an angle (θ) of 40° up from the horizontal. A rope parallel to the incline connects the disk to an immovable wall. Through experiment, it is found that the static friction between the disk and the incline is at a maximum. 

(a) What is the tension in the rope? 

(b) What is the coefficient of static friction between the disk and the incline?