The local bookstore must determine how many of each of the four new books on photonics it must order to satisfy the new interest generated in the discipline. Book 1 costs $60, will provide a profit of $12, and requires 3 inches of shelf space. Book 2 costs $75, will provide a profit of $10, and requires 4 inches of shelf space. Book 3 costs $100, will provide a profit of $8, and requires 2 inch of shelf space. Book 4 costs $65, will provide a profit of $15, and requires 2 inches of shelf space. Find the number of each type that must be ordered to maximize profit. Total shelf space is 150 inches. Total amount available for ordering is $4000. It has been decided to order at least 10 Book 2. (1) Establish the model of the optimisation problem (LP with 4 variables). State clearly in words what the decision variables are, what the objective function and the equation/inequality constraints represent.