What i'm going to do is give you the questions as well as the answers. i need you with understanding the reasons behind their answers. no matter what i do i cant seem to get what they've gotten as answers.

part a: how much energy does the electron have initially in the n=4 excited state?
−1.36×10^−19

part b: what is the change in energy if the electron from part a now drops to the ground state?
−2.05×10^−18

part c: what is the wavelength lambda of the photon that has been released in part b?
9.72×10^−8

Under what conditions will a gas be most likely to exhibit the ideal gas properties predicted by the ideal gas law? 1)high pressures and high temperature, because particles are forced closer together with higher kinetic energy, so intermolecular forces of attraction are weaker 2)high pressure and low temperature, because particles are forced closer together and moving slower, so the volume of the particles is less significant 3) low pressure and high temperature, because particles are spread farther apart and moving faster, so the intermolecular forces of attraction are weaker 4)low pressure and low temperature, because particles are spread farther apart with lower kinetic energy, so the volume of the particles is less significant