(* Single EOQ with All-Units Discounts *);



<<Pws.m

demand = 12500; setup = 125; holding = 0.36;

price =

  PWSFreeze[

    PWS[{{{1, IB[600]}, 35.5 &},

        {{600, IB[1000]}, 33.72 &},

        {{1000, IB[2000]}, 31.45 &},

        {{2000, Infinity}, 28.5 &}}]]



totalCost =

    (demand setup/#) & + demand price + (holding #/2 &) price;

totalCost // PWSForm

Plot[totalCost[q], {q, 1, 3000},

    PlotRange -> {350000, 550000},

    AxesLabel -> {"Quantity", "Cost"}];



tC = totalCost /. Infinity -> 9999;

FindMinimum[tC[q], {q}]



demand = 5640;

price = PWSFreeze[PWS[{{{1, IB[600]}, 41.2 &},

        {{600, IB[1000]}, 41.10 &},

        {{1000, IB[2000]}, 41.07 &},

        {{2000, Infinity}, 41.004 &}}]]

totalCost = (demand setup/#) & + demand price + (holding #/2 &) price;

Plot[totalCost[q], {q, 1, 3000},

    PlotRange -> {220000, 270000},

    AxesLabel -> {"Quantity", "Cost"},

    PlotStyle -> {{}, {Dashing[{0.01}]}}];

tC = totalCost /. Infinity -> 9999;

FindMinimum[tC[q], {q}]