set PROD;  # products

param rate {PROD} > 0;     # tons produced per hour
param avail >= 0;          # hours available in week

param profit {PROD};       # profit per ton
param market {PROD} >= 0;  # limit on tons sold in week

var Make {p in PROD} >= 0, <= market[p]; # tons produced

maximize Total_Profit: sum {p in PROD} profit[p] * Make[p];

               # Objective: total profits from all products

subject to Time: sum {p in PROD} (1/rate[p]) * Make[p] <= avail;

               # Constraint: total of hours used by all
               # products may not exceed hours available