A problem by catherine almira
A farmer intends to buy more ducks and chickens. He has to pay $4 for each duck and $3 for each chicken. He has to spend $1 on the feed for each duck and $2 for each chicken after which he will be able to sell the ducks and chickens at $6 each. He has only $36 with which to buy the poultry and $20 to buy feed. How much is the maximum profit?