In response to complaints about high prices, a grocery chain runs the following advertising campaign: "If you pay your child $3 to go buy $100 worth of groceries, then your child makes twice as much on the trip as we do." You've collected the following information from the grocery chain's financial statements: a. What is the profit margin for the child as a percentage of what they spend and the profit margin for the store? (Do not round intermediate calculations and enter your answers as a percent rounded to 2 decimal places, e.g., 32.16.) b. What is the store's ROE? (Do not round intermediate calculations and enter your answer as a percent rounded to 2 decimal places, e.g., 32.16.)