I need help coming up with a smart formula to use in Excel that I can type once and copy throughout the yellow section. Can you also explain how the formula is made for future reference? Just need help with question A.

(a) Gross monthly sales and monthly sales' return are given in Table 9 below, compute cumulative sales using Formula with appropriate cell references. Write a formula in cell E103 to calculate "Year to Date Cumulative Net sales" based on the "Gross Monthly Sales" and "Sales' Return" in Table 10 (C103:0114). Apply the "Gross Net Sales" (C103) and "Sales' Return" (D103) to determine the "Year To Date Cumulative Net Sales" in cell E103 and copy over and down through to cell E114. You should write a formula such that when the formula is copied, it computes the "Year To Date Cumulative Net Sales" amount correctly. Hint : Please go through the Learning Exercise 8.6, a similar exercise was solved. (b) Apply Conditional Formatting to the range C103:0114 (Gross Monthly Sales), Add 3 Arrows (colored) icon sets. Month January February March April May June July August September October November December Table 9: Cumulative Net sales Year to Date Gross Monthly Sales Sales' Return Cumulative Net sales $ 80,650 $ 6,950 $ 100,800 $ 7,300 $ 106,250 $ 6,200 $ 94,450 $ 8,050 $ 90,800 $ 8,800 $ 103,350 $ 6,550 $ 108,350 $ 5,300 $ 101,250 $ 6,800 $ 101,800 $ 5,700 $ 140,000 $ 10,000 $ 150,000 $ 9,000 $ 130,000 $ 9,050