Krystal Clear Replacement Windows and Doors (SRW) need to plan door production for the following week. The time required for each door to go through the two stages of production is given in Figure 2. The first stage is plastic moulding and the second stage is the production shop. The total amount of plastic needed for each door is also given in Figure 2.

	Small	Large	X Large	Available
Plastic Moulding (hours)	0.58	0.55	0.6	120
Finishing Shop (hours)	0.09	0.15	0.16	24
Plastic (Kg)	0.4	0.5	0.6	110
Profit (£)	38	48	52

Figure 2:

1. Formulate the problem using the linear programming (LP) technique. State clearly your variables, constraints and optimising function.

(4 Marks)

1. Solve the LP problem using Excel and the solver function and give the integer solution that optimises the profit.

(4 Marks)

1. To replenish stock levels at least 40 of each size must be produced. Find the revised optimum profit level?

(4 Marks)

1. Keeping the minimum production levels at 40. Overtime is increased in both the plastic moulding department and the finishing shop in an attempt to increase production. This means that there is 15% more hours available in both departments. What is the new optimum profit level?

(4 Marks)

1. The amount of plastic is now a limiting factor. Run several scenarios and critically evaluate how the amount of plastic available affects the profit margin.