To move a large crate across a rough floor, you push on it with a force F at an angle of 21 degrees below the horizontal.

Q.Find the force necessary to start the crate moving, given that the mass of the crate is 32 kg and the coefficient of static friction between the crate and the floor is 0.59.

I thought I could solve for N by N=mgcos(theta) but I think I have it all wrong.

Help?