A thin steel cable with 2.0 mm diameter is hooked up to a vibrating device, which exerts a tension of 8.5 N on the cable. The device vibrates at a frequency of 70.0 Hz, producing waves in the cable with an amplitude of 0.50 cm. Calculate the power output of this device, assuming the waves do not reflect back along the cable. (The density of steel is ρ_steel=7800 kg/m³).