Consider the following data that illustrates demand and production costs for a given product. Jan Feb Mar Apr 150 175 200 120 Demand (units) Production Cost (S/unit) 30 35 20 25 Inventory carrying costs are estimated at $4 per unit per month. The firm wants to produce at least 50 units per month to uniformly utilize its existing resources, and the production capacity of this firm is 160 units per month. Assume that the beginning inventory is 45, and the inventory holding cost for this 45 units has been accounted at the previous year. Formulate a model to determine how many units of the product should be produced monthly to meet the expected demand at minimal cost. (a) Formulate a model for this problem, taking care to define each of the variables used. (b) Solve the model using Excel. (c) State the recommendation.