A body is sliding down an inclined plane having coefficient of friction 0.5. If the normal reaction is twice that of the resultant downward force along the inclination the angle between the inclined plane and the horizontal is

A body is sliding down an inclined plane having coefficient of friction 0.5 .If the normal reaction is 4 times that of the resultant downward force along the incline, find the angle between the inclined plane and the horizontal.