19 In cell E1, insert the CUMIPMT function to calculate the cumulative interest. Use cell references to calculate the periodic rate, nper, present value (price) starting period, and ending period. Make sure the function returns a positive value. 20 In cell E2, insert the CUMPRINC function to calculate the cumulative principal through the sixth month payment. Use cell references for all arguments. Make sure the function returns a positive value. = CumpR NC