Five Electrons Are in a Two-Dimensional Square Potential Energy Well

Multiple Choice

Five electrons are in a two-dimensional square potential energy well with sides of length L.The potential energy is infinite at the sides and zero inside.The single-particle energies are given by where n_x and n_y are integers.The energy of the first excited state of the system is:

A) 13 (h²/8mL²)
B) 22 (h²/8mL²)
C) 24 (h²/8mL²)
D) 25 (h²/8mL²)
E) 27 (h²/8mL²)