Purple Swift manufactures birdhouses in lots of 10. Each birdhouse takes 45 minutes to paint. After 10 birdhouses are painted, the company switches paint color which requires a one hour changeover. Assume that the company should changeover at the very beginning of the process. The company works 8 hours per shift, one shift per day, 215 days per year. Currently the company has one point booth. What is Purple Swift's paint capacity cushion if it builds 1,800 birdhouses per year? Purple Swift's paint capacity cushion is ___%