2. WW equation for inltration capacity is f i (r) = Bf" (a) Aside from the fault that this predicts f" = 0 at large time, what is the smallest physically reasonable value of it? Use only the most general facts about the time behavior of f\" to reach an answer. (b) Let 1"" denote the time integral off". Determine F*(r). (c) On the basis of your answer to (b), what is the physically reasonable maximum value of n? (d) Derive an equation for inltration capacity as a function of actual cumulative inltration (F, not F\"), valid for any rainfall, pm. In order to do this, what assumption must be made regarding the original inltration equation? (e) Derive expressions for ponding time due to rainfall of constant intensity pa, and the post-ponding inltration rate