7. The zombie apocalypse has just started and you are on your way down a back road when you come to a huge tree blocking your path. You find a pretty thick looking branch and use it as a lever to clear the road. You put in 188J of work on the branch and the branch in turn puts out 109J of work on the fallen tree. What is the efficiency of the make shift lever? What happened to the rest of the energy that was put in to the branch, why is it not 100% efficient?