The Positrons Emitted from the Galactic Center Can Be Detected

The positrons emitted from the galactic center can be detected because they annihilate with electrons and emit gamma rays.Two gamma rays are produced in such a situation to conserve both energy and momentum.Suppose the positron and electron,each with energy mc²,convert all of this energy into two identical gamma ray photons.What will be the wavelength of these photons?

A) 1.5 × 10-² nm
B) 2.4 × 10-³ nm
C) 3.9 × 10-⁴ nm
D) 7.9 × 10-⁵ nm