What are the factors that affect the efficiency of a simple machine?​

Can someone explain to me how to do this problem ?

Which of the following best describes internal energy? a. the difference between the kinetic and potential energies of the particles in a system b. the sum of the kinetic and potential energies of the particles in a system c. the sum of the kinetic and thermal energies of the particles in a system d. the difference between the kinetic and thermal energies of the particles in a system

How is the ideal mechanical advantage of a wheel and axle calculated?