In response to complaints about high prices, a grocery chain runs the following advertising campaign: If you pay your child $6 to go buy $50 worth of groceries, then your child makes twice as much on the trip as we do. Youve collected the following information from the grocery chains financial statements: (millions) Sales $ 509

Net income 23

Total assets 489

Total debt 397

What is the profit margin for the store? (in %) (rounded to 4 decimal places)