4. The sales rep commission rate varies for each sales rep. In column E, Laura used a VLOOKUP function to look up the commission rate for each sales rep and then multiplied the commission rate by the invoice amount to calculate the commission. Although the first row in column E of the Excel table named Aging displays the correct commission, all the other cells display a number, -, or #N/A. Find the problem with the formulas in the Commission column and fix it.