1. The problem statement, all variables and given/known data A climber's gravitational potential energy increases from 14000 J to 21 000 J while climbing a cliff. She expends 18 000 J of energy during this activity. What is the efficiency of this process? 2. Relevant equations Efficiency= useful output/ total input Total energy before = total energy after 3. The attempt at a solution Well, I've been able to solve all other efficiency/ conservatino of energy questions but for some reason I just don't understand this one. I don't understand what to consider as the input or the useful output energy. Thanks for your help!