Product A requires 9 minutes of milling, 7 minutes for inspection, and 6 minutes of drilling per unit; product B requires 10 minutes of milling, 5 minutes for inspection, and 8 minutes of drilling per unit; product C requires 7 minutes of milling, 3 minutes for inspection, and 15 minutes of drilling. The department has 20 hours available during the next period for milling, 15 hours for inspection, and 24 hours for drilling. Product A contributes $2.5 per unit to profit, product B contributes $7.4 per unit, and product C contributes $4.4 per unit. How many constraints are there in the Linear Programming Formulation of this problem? HINT: Don't forget to count each one of the non-negativity constraints as well. b.4 O c.5 d. 6 e. 7 1.8 9.9