Several ores are blended to a final product that must have a certain quality ('grade'). We wish to determine the quantity of every ore to be used in the blend with the objective to maximize the total profit (calculated as sales revenues - raw material cost).

Further explanation of this example: 'Xpress Python Reference Manual'

# Data file for 'blend.py'
COST = [85, 93]
AVAIL = [60, 45]
GRADE = [2.1, 6.3]