You are riding in a school bus. As the bus rounds a flat curve at constant speed, a lunch box with mass O.SOO kg, suspended from the ceiling of the bus by a string 1.80 m long, is found to hang at rest relative to the bus when the string makes an angle of 30.00 with the vertical. In this position the lunch box is SO.O m from the center of curvature of the curve. What is the speed v of the bus?