An Electron Is Confined in a Two-Dimensional Box Where U(x,y)=

An electron is confined in a two-dimensional box where U(x,y) = 0 for x = 0 to L and y = 0 to 3L,and U(x,y) = infinity outside these boundaries.If L = 0.5 nm,then calculate the energy of the first excited state.

A) 1.7 eV
B) 2.2 eV
C) 6.2 eV
D) 3.0 eV
E) None of these is correct.