A power plant stores a spare filter cartridge whose stock follows the saw-tooth pattern in the figure (instant replenishment, uniform use, no shortages). The annual demand, ordering cost, unit price and holding-cost rate are given on the figure. Determine (a) the economic order quantity (answer in units), (b) the number of orders per year (answer in orders/yr) and (c) the total annual inventory cost, i.e. ordering cost plus holding cost, excluding purchase cost (answer in Tk).