A uniform window that is 0.700 m long and 0.500 m wide has a mass of 11.0 kg. The window is pivoted by frictionless hinges along its width and allowed to hang vertically. A 0.850 kg unlucky peregrine falcon has a level flight speed of 100 km/h when it hit the window at its center. The falcon bounces back at a speed of 60 km/h. Calculate the window's angular speed immediately after its hit by the unlucky falcon.