A boat builder has the capacity to make both 20 metre and 40 metre boats. They can make up to 3 of the short ones, or three of the long ones, but in total they can make no more than four boats. It takes 240 person days to make a short boat, and 440 person days to make a long boat. This season, they will have 1060 person-days available. After deducting variable costs the short boats have a revenue of $30,000 per boat, while the long ones have a revenue of $51,000 per boat.

(a) Formulate an integer model for this problem.

(b)Solve by the graphical method to determine the best integer solution.