Dexter Eius is running through the cafeteria when he slips on some mashed potatoes and falls to the floor. (Let that be a lesson for Dexter.) Dexter lands in a puddle of milk and skids to a stop with an acceleration of -4.8 m/s/s. Dexter weighs 780 Newtons. Determine the coefficient of friction between Dexter and the milky floor.