Solve the linear programming problem
A manufacturer of golf clubs makes a profit of $60 per set on a model A set and $40 per set on a model B set. Daily production of the model A clubs is between 30 and 60 sets, inclusive, and that of the model B clubs is between 20 and 30 sets, inclusive. The total daily production is not to exceed 60 sets. How many sets of each model should be manufactured per day to maximize the profit?