Apoint source emits s n/s isotropically in an infinite vacuum in steady state general hint: this is not a diffusion problem - a vacuum is certainly not a) show that the scalar flux at a distance r from the source is exactly s/a4tr] hint: think of a very very thin spherical shell of inner radius r, outer radius r + dr. at what rate do neutrons make tracks in this shell? how many neutrons per second enter this shell? how far does each one go in the shell? at what rate per unit volume? exactly what is the net current density at a distance r from the source? hint: at what rate do neutrons leak through a spherical surface of radius ? what st the net current density be to produce this leakage rate? b) repeat problem 5 given a medium with absorption but no scattering or fission. (hint: this just throws in an attenuation factor.)