set PROD; # products set AREA {PROD}; # market areas for each product param T > 0; # number of weeks param rate {PROD} > 0; # tons per hour produced param inv0 {PROD} >= 0; # initial inventory param avail {1..T} >= 0; # hours available in week param market {p in PROD, AREA[p], 1..T} >= 0; # limit on tons sold in week param prodcost {PROD} >= 0; # cost per ton produced param invcost {PROD} >= 0; # carrying cost/ton of inventory param revenue {p in PROD, AREA[p], 1..T} >= 0; # revenue per ton sold var Make {PROD,1..T} >= 0; # tons produced var Inv {PROD,0..T} >= 0; # tons inventoried var Sell {p in PROD, a in AREA[p], t in 1..T} >= 0, <= market[p,a,t]; # tons sold maximize total_profit: sum {p in PROD, t in 1..T} (sum {a in AREA[p]} revenue[p,a,t]*Sell[p,a,t] - prodcost[p]*Make[p,t] - invcost[p]*Inv[p,t]); # Total revenue less costs for all products in all weeks subject to time {t in 1..T}: sum {p in PROD} (1/rate[p]) * Make[p,t] <= avail[t]; # Total of hours used by all products # may not exceed hours available, in each week subject to initial {p in PROD}: Inv[p,0] = inv0[p]; # Initial inventory must equal given value subject to balance {p in PROD, t in 1..T}: Make[p,t] + Inv[p,t-1] = sum {a in AREA[p]} Sell[p,a,t] + Inv[p,t]; # Tons produced and taken from inventory # must equal tons sold and put into inventory