solve using LP and Lingo

4. Homework 7 A vacuum cleaner manufacturer tries to "plan ahead" in order to effectively address the seasonal variation appearing in the annual demand of its products. A planning horizon of 6 months is used. The (aggregate) demand forecast for the next six months along the number of working days are as follows: The associated cost break-down is as follows: Starting and Operating Conditions: Note 1: we should compute the net requirements production of each month. The ending inventory of a month should equal at least to 25% of the corresponding month. The obtained production requirement will be applied in each aggregate plan. Note 2; we should verify that: - The production unit cost is $175 per unit, because the material cost is $100 per unit and the regular labor cost is (5$15=75). - The unit cost of subcontracting is $215 m production unit cost + marginal subcontracting = $175+$40. - The unit cost of stock-out is only $60. The production unit cost will be added later