set MAT;             # materials
set ACT;             # activities

param io {MAT,ACT};  # input-output coefficients

set MATF within MAT; # finished materials

param revenue {MATF} >= 0;

param sell_min {MATF} >= 0;
param sell_max {i in MATF} >= sell_min[i];

param cost {ACT} >= 0;
param act_min {ACT} >= 0;
param act_max {j in ACT} >= act_min[j];

maximize Net_Profit;

subject to Balance {i in MAT}: to_come = 0;

var Run {j in ACT} >= act_min[j], <= act_max[j],
   obj Net_Profit -cost[j],
   coeff {i in MAT} Balance[i] io[i,j];

var Sell {i in MATF} >= sell_min[i], <= sell_max[i],
   obj Net_Profit revenue[i],
   coeff Balance[i] -1;