Repeat problem S64a using flexible bus routes instead of fixed bus routes, with demand density T reduced from 600 to 10trips/mi2hour. Optimize the combination of zone area and headway for each flexible route. If you prefer you can work with frequency (F= 1/h) instead of headway and number of zones N, which is also the number of routes instead of zone area A. (N = 6*2/A.) You may assume that all areas and headways are equal for all zones. Thus for each bus tour n = hAT/g, where h = headway , A = zone area, T = demand density and g = average group size (e.g. passengers per stop, which = 1.0 in problem S64d