A power electronics device has an on-state power loss of 40 W and switching loss in watts equal to 1.1 × switching frequency in kilohertz. The junction to case thermal resistance is 1.85°C/W, and the maximum allowable junction temperature T_jmax is 150°C. If the device case is mounted on a heat sink to limit the case temperature to 50°C, determine the maximum allowable switching frequency for this device on this heat sink.