I don't know what to do in question 9 homes of dreams microsoft excel 2013page 186

Revise your formulas in cells C21, E21, and G21, nesting them within an IF formula. For each cell, test whether the value of cell B21 is not equal to (a blank). If it is not, return the value of the VLOOKUP function in cells C21 and E21 and the calculated value in cell G21. Otherwise, those cells should return a blank () value. 10. 10. Use AutoFill to copy the formulas in cells C21, E21, and G21 through row 30 in the order items table