Company X produces item Y. Setting up each production run for Y costs $2500. Insurance costs, based on average number of Y in warehouse, is $20 per item per year. Storage costs, based on the maximum number of Y in the warehouse, is $15 per item per year. Suppose that company X expects to sell 1600 items of Y at a fairly uniform rate throughout the year. Determine the number of production runs that will minimize the company's total expenses.