In a Particular Case of Compton Scattering,a Photon Collides with a Free

In a particular case of Compton scattering,a photon collides with a free electron and scatters backwards.The wavelength after the collision is exactly double the wavelength before the collision.What is the wavelength of the incident photon? (m_el = 9.11 × 10^-31 kg, h = 6.626 × 10^-34 J ∙ s,c = 3.00 × 10⁸ m/s)

A) 3.6 pm
B) 4.8 pm
C) 2.4 pm
D) 1.2 pm
E) 6.0 pm