Calculate the electrostatic force when one of the balloons is reduced to 2×10^-9 C and held at a separation distance of 2 m! please help☺️

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