Two skaters of equal mass skate toward each other, each moving at 4 m/s. Their lines of motion are separated by a perpendicular distance of 2.5 m. Just as they pass each other (still 2.5 m apart), they link hands and spin about their common center of mass. What is the rotational speed of the couple about the center of mass? Treat each skater as a particle. Draw a picture before and after the collision and start from the first principle.