2) (20 p.) Consider an infinite planar source emitting S fast neutrons per cm sec in an infinite diffusing medium in which no up-scattering occurs. You can also neglect absorption in the fast region. Please write the relevant differential equations for the fast and thermal groups and solve them considering the following parameters: LT2: Thermal diffusion area TT: Neutron age D: Diffusion coefficient for the thermal group D: Diffusion coefficient for the fast group : Thermal absorption cross-section 12: Transfer cross-section Note: You should indicate all the conditions that you take into account for calculating the unknown coefficients.