e slab of ssile material has thickness L. The neutrondensity n(x; t) in the material obeys the [email protected]@t= [email protected]@x2+ n + ;where n(x; t) is zero at the surface of the slab at x = 0 and L. Here D is the neutrondiusion constant, the term n describes the creation of new neutrons by induced ssion,and the constant is the rate of production per unit volume of neutrons by spontaneousssion.(a) Expand n(x; t) as a seriesn(x; t) =Xmam(t)’m(x) ;where ‘m(x) are a complete set of functions you think suitable for solving the prob-lem.1