(a) Find the radius of the n = 4 Bohr orbit of a doubly ionized lithium atom (Li2+, Z = 3).

(b) Is the energy required to raise an electron from the n = 4 state to the n = 5 state in Li2+ greater than, less than, or equal to the energy required to raise an electron in hydrogen from the n = 4 state to the n = 5 state? Explain.

(c) Verify your answer to part (b) by calculating the relevant energies.