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Ring-Ring Phone Ltd. manufactures luxury cell phones. Their demand for the next 6 months is 100, 250, 190, 140, 220, and 110 cell phones, respectively. The production costs are not constant, but they change on a monthly basis. In this case, the cost per unit produced is $50, $45, $55, $48, $52, and $50 for the following 6 months. The company has the option to produce units in previous months and sell them later (for instance, they can produce 5 cell phones in April and sell them in May). However, doing so carries an inventory holding cost of $8 per cell phone per month. In the first month, the company does not have any cell phone in stock. Ring-Ring Phone Ltd. has asked you to formulate (not solve) an LP to determine a production schedule that minimizes total costs for the next 6 months