4. Integer Programming Models. (15 points modeling+5 points question) Glueco produces two types of glue on three different production lines. Each line can be utilized by up to 7 workers at a time. Workers are paid $600 per week on production line 1, $800 per week on production line 2, and $1000 per week on production line 3. A week of production costs $1000 to set up production line 1, $1500 to set up production line 2, and $2000 to set up production line 3. During a week, on production line 1, each worker produces 20 units of glue 1 and 25 units of glue 2; on production line 2, each worker produces 30 units of glue 1 and 30 units of glue 2; on production line 3, each worker produces, 50 units of glue 1 and 35 units of glue 2. Each week, at least 120 units of glue 1 and at least 150 units of glue 2 must be produced. Formulate an IP to minimize the total cost of meeting weekly demands. 4.1) Following the 5 steps introduced in class, model the above problem. Do not solve. 4.2) (Please add the following requirement after modeling, you do not need to write the whole model again) Instead of using any combination of production lines, you can use at most two production lines