You need to be able to compute atom densities in order to compute macroscopic xs. consider neutrons incident normal to an infinite slab of thickness 3l consistent of two regions. the first region of thickness 2l is filled with ordinary water (ph,0 = 1 g/cm, 1 = 38 b, 2 = 6.8 b, 070-16 = 0.178 mb, natural abundance of h-2 (deuterium) in hydrogen is 0.0115%). the second region is filled with uranium metal enriched to 95 w% in u-235 (pu = 19.1 g/cm, 0735680.6 b, 07*8 = 2.7 b). (a) (10 pts) determine the atom densities (at/cm) of h-1, h-2, and o. (b) (10 pts) determine the atom densities (at/em of u-235, and u-238. (c) [2.5+2.5 pts) compute the macroscopic cross section in each region. (d) (3 pts) find the uncollided beam intensity at l, 2l, 3l when l=0.2 cm (e) (1+2+2 pts determine the probability of first interaction in each region.