Up, Up, and Away is a producer of kites and wind socks. Relevant data on the bottleneck operation in the shop for the upcoming fiscal year are given in the following table: i Item Demand forecast Lot size Kites 28,000 units/year 25 units Standard processing time Standard setup time 0.4 hour/unit 3.0 hours/lot Wind Socks 15,000 units/year 80 units 0.8 hour/unit 4.0 hours/lot The shop works two shifts per day, 8 hours per shift, 220 days per year. Currently, the company operates four machines, and desires a 25 percent capacity cushion. How many machines should be purchased to meet the upcoming year's demand without resorting to any short-term capacity solutions? The number of additional machines required is . (Enter your response rounded up to the next whole number.)