First you need to find total mechanical energy which is kinetic energy+potential energy, or (1/2mv^2+mgh). Since there is no height, we can pretty much ignore the potential energy and just calculate the kinetic.
1/2mv^2=1/2(64)(3.4)^2= 369.92J. Since it says the speed is 0 at the end of the run, we can assume that all the mechanical energy was lost. Therefore, 369.92 J of energy was lost
