An electron in a hydrogen atom makes a downward transition from the $n=9$ level to the $n=2$ level. What is the wavelength of the emitted photon?

a$)410\mathrm{.}2$ nm

b$)397\mathrm{.}0$ nm

c$)388\mathrm{.}9$ nm

d$)383\mathrm{.}6$ nm