A centrifuge is a common laboratory instrument that separates components of differing densities in solution. This is accomplished by spinning a sample around in a circle with a large angular speed. Suppose that after a centrifuge in a medical laboratory is turned off, it continues to rotate with a constant angular deceleration for 10.4 seconds before coming to rest. If its initial speed was 3870 rpm, what is the magnitude of its angular deceleration? How many revolutions did the centrifuge complete after being turned off?