set PROD;                  # a set of products

# parameters
param profit {PROD};       # unit profit 
param usage  {PROD} > 0;   # unit usage of material
param avail >= 0;          # available material (wood)
param demand {PROD} >= 0;  # market demand limit

# variables: quantities to produce
var make {p in PROD} >= 0, <= demand[p]; 

# Objective: total profits from all products
maximize total_profit: sum {p in PROD} profit[p] * make[p];

# Constraint: total use of material by all
# products may not exceed the available
subject to Availability: 
sum {p in PROD} usage[p] * make[p] <= avail;