Suppose two children push horizontally, but in exactly opposite directions, on a third child in a sled. The first child exerts a force of 78 N, the second a force of 93 N, kinetic friction is 5.5 N, and the mass of the third child plus sled is 20.5 kg.

 

Using a coordinate system where the second child is pushing in the positive direction, calculate the acceleration in m/s2