In response to complaints about high prices, a grocery chain runs the following advertising campaign: "If you pay your child $1 to go buy $30 worth of groceries, then your child makes about 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 child's profit margin? Note: Do not round intermediate calculations and enter your answer as a percent rounded to 2 decimal places, e.g, 32.16. b. What is the store's profit margin? Note: Do not round intermediate calculations and enter your answer as a percent rounded to 2 decimal places, e.g., 32.16 . c. What is the store's ROE? Note: Do not round intermediate calculations and enter your answer as a percent rounded to 2 decimal places, e.9., 32.16