20. Julie James is opening a lemonade stand. She believes the fixed cost per week of running the stand is $50.00. Her best guess is that she can sell 300 cups per week at $0.50 per cup. The variable cost of producing a cup of lemonade is $0.20. a. Given her other assumptions, what level of sales volume will enable Julie to break even? b. Given her other assumptions, discuss how a change in sales volume affects profit. c. Given her other assumptions, discuss how a change in sales volume and variable cost jointly affect profit. d. Use Excel's Formula Auditing tools to show which cells in your spreadsheet affect profit directly