2. A farmer must decide how many cows and how many pigs to purchase for fattening. He realizes a net profit of $40.00 on each cow and $20.00 on each pig. Cows eat three bushels of feed per week and pigs eat one per week. On the average, farmer Ben can grow and harvest no more than nine bushels per week. He has decided to purchase at least four animals, but the number of cows will not exceed four and the number of pigs will not exceed six. He wants to know the most profitable mix of cows and pigs to buy.