Work is equal to the force applied times the displacement. Since you pull the wagon at constant speed this means that there is no acceleration on the wagon as it does not change speed. F=ma. Since a=0, F=0. Therefore no work has been done in this situation
Kinetic energy=1/2mv^2
=1/2(142*10^-3)(42.9)^2=130.6=131J
The denser the medium, the harder the sound struggles to travel through. The medium will determine how effectively the sound will travel, for example, large bodies of water has barely any sound for its density.