To give a 18-{\rm kg} child a ride, two teenagers pull on a 3.6-{\rm kg} sled with ropes, as indicated in the figure .

To give a 18-{rm kg} child a ride, two teenagers pull on a 3.6-{rm kg} sled with ropes, as indicated in the figure . Both teenagers pull with a force of 55 {rm N} at an angle of 35 ^circ relative to the forward direction, which is the direction of motion. In addition, the snow exerts a retarding force on the sled that points opposite to the direction of motion, and has a magnitude of 57 {rm N}.Find the acceleration of the sled and child.