Shelley Company produces a machine that requires three pistons. They feel that they must produce 200,000 machines next year. They want to hold, in their ending materials inventory, enough pistons to meet 20% of next year's production requirement. They will start the year with enough pistons to manufacture 20,000 machines. How many pistons must they purchase? 660,000 710,000 690,000 645,000 615,000