Bonnie and Clyde are sliding 450 {\rm kg} bank safe across the floor to their getaway car.

Bonnie and Clyde are sliding 450 {rm kg} bank safe across the floor to their getaway car. The safe slides with a constant speed if Clyde pushes from behind with 420 {rm N} of force while Bonnie pulls forward on a rope with 285 {rm N} of force. What is the safe's coefficient of kinetic friction on the bank floor?