A 40 kg boy and a 40 kg sled are on the frictionless ice of a frozen lake, 10 m apart and connected by a rope of negligible mass. Both the boy and the sled are initially at rest. The boy exerts a constant horizontal force of 10 N on the rope. What is the magnitude of the acceleration of the sled? (take g = 10 m/s2) O 0.5 m/s2 O 0.125 m/s2 O 1.25 m/s2 O 0.25 m/s2 O 0.75 m/s2