1. Estimate the fast group constants characterizing H2O if the fast group is taken from E1 = 1 eV to E0 = 10MeV and the neutron energy spectrum over this group is taken as ?(E) =1/E.
2. Estimate the minimum group spacing that will yield directly coupled multi-group equations for 12C, 2D, 9Be, and 22Na.
3. What percentage of the neutrons slowing down in hydrogen will tend to skip groups if the group structure is chosen such that Eg-1=Eg = 100 ?

4. Write out the detailed form of the multi-group diffusion equation for a four-group model in which:
(a) there is direct coupling;
(b) the fission source exists only in the upper two groups;
(c) only the lowest group contains thermal neutrons.