An 11.8 eV photon is absorbed by an electron in an atom, causing the electron to be excited from level 1 to level 3. The electron then emits a 4.1 eV photon and shifts to level 2. What photon will be emitted when the electron moves back to level 1?

a. 15.9 eV
b. 11.8 eV
c. 7.7 eV
d. 4.1 eV