First label columns A, B, and C, Sales, Plan A, and Plan B, respectively. Enter 400 into cell A2. Then enter the formula, =120+10%*A2, into cell B2. Finally, enter the formula, =90+15%*A2 into cell C2. This spreadsheet will compute your pay for the two plans if you average $400 in sales each week.
To do the computation for weekly sales from November through mid-January, enter the weekly sales amounts into the Sales column. Use Fill Down to copy the formulas in the Plan A and Plan B columns. You may also want to insert a column for the week number or dates. Your total earnings for Plan A would be $1875 and for Plan B, $1822.50. Plan A is again better.
What would sales have to be for a week to make Plan B better?