[tex]\Delta E=|E_{2}-E_{3}|=|\frac{E_{1}}{4}-\frac{E_{1}}{9}|=|\frac{-13.9eV}{4}-\frac{-13.9eV}{9}|=\\\\
=|-3.475eV+1.544eV|=|-1,931eV|=1.931eV[/tex]
1eV --------- is ----------- 1.6*10⁻¹⁹J
1.931eV ---- is ----------- x
x = [1.931eV*1.6*10⁻¹⁹J]/1eV ≈ 3,1*10⁻¹⁹J
ANSWER E