A chair of weight 125 lies atop a horizontal floor; the floor is not frictionless. You push on the chair with a force of = 42.0 directed at an angle...

A chair of weight 125 lies atop a horizontal floor; the floor is not frictionless. You push on the chair with a force of = 42.0 directed at an angle of 39.0below the horizontal and the chair slides along the floor.Using Newton's laws, calculate , the magnitude of the normal force that the floor exerts on the chair.