A 4.0kg crate is placed on a rough plank that makes an angle of 22∘ with the horizontal. The crate is observed to be on the verge of sliding down.
(i) Determine the coefficient of static friction between the crate and the plank.
(ii) While the plank is still at the same angle, a worker wants to keep the crate at rest by pulling it upward along the plane with a force F acting parallel to the surface. Find the least magnitude of F that will accomplish this.