Oone o3 in the atmosphere filters ultraviolet light from

Question

Ozone, O₃, in the atmosphere filters ultraviolet light from the sun because light with wavelength less than 300 nm breaks the oxygen-oxygen bond. What is the oxygen-oxygen bond energy (kJ/mol) in ozone?  (h=6.63×10^-34 J·s , c=3×10⁸ m/s)

A. 318 kJ/mol

B. 399 kJ/mol

The correct answer is (b) 399 kJ/mol. I wonder how to get this result.