(* ------------------------------------------------------------ *) 
 (*  heat1 . nb  [
            ma4]   Math 371 2.16                            *) 
 (* ------------------------------------------------------------ *)

u[x_, t_]  :=  
      60  +  Sum[((400*(-1)^(n + 
                            1)/((Pi^2)*(2*n - 1)^2) - 
                  240/((2*n - 1)*Pi)))
* 
            Sin[(2*n - 1)*Pi*x/20]*
            Exp[-t*((2*n - 1)*Pi/20)^2], {n, 100}]

Plot[u[x, 0], {x, 0, 10}, PlotRange -> {0, 100}]

Plot[u[x, 0.01], {x, 0, 10}, PlotRange -> {0, 100}]

Plot[u[x, 0.1], {x, 0, 10}, PlotRange -> {0, 100}]

Plot[u[x, 1], {x, 0, 10}, PlotRange -> {0, 100}]

Plot[u[x, 5], {x, 0, 10}, PlotRange -> {0, 100}]

Plot[u[x, 20], {x, 0, 10}, PlotRange -> {0, 100}]

Plot[u[x, 100], {x, 0, 10}, PlotRange -> {0, 100}]