A 100-Kg Box Is Placed on a Ramp $\degree$ What Is the Coefficient of Static Friction Between Box and of the Ramp

A 100-kg box is placed on a ramp.As one end of the ramp is raised,the box begins to move downward just as the angle of inclination reaches 15 $\degree$ .What is the coefficient of static friction between box and ramp?

A) 0.15
B) 0.27
C) 0.77
D) 0.95