A car of mass \(m\) travels at a constant speed \(v\) around a frictionless circular track of radius \(R\). The track is banked at an angle \(\theta\) relative to the horizontal such that the car does not slide up or down the ramp. Let \(a_c\) represent the magnitude of the car's centripetal acceleration. Which of the following expressions correctly represents the magnitude of the normal force \(F_N\) exerted by the track on the car?