Calculate the Wavelength, in Nanometers, of the Light Emitted by a Hydrogen

Calculate the wavelength, in nanometers, of the light emitted by a hydrogen atom when its electron drops from the n = 7 to the n = 4 principal energy level. Recall that the energy levels of the H atom are given by E_n = -2.18 × 10^-18 J (1/n²) . (c = 3.00 × 10⁸ m/s; h = 6.63 × 10^-34 J • s)

A) 4.45 × 10^-20 nm
B) 2.16 × 10^-6 nm
C) 9.18 × 10^-20 nm
D) 1.38 × 10¹⁴ nm
E) 2.17 × 10³ nm