Can someone please tell how they got "N" in the question

Question 6 1.5 / 5 point Scheduled payments of $1,000 due today and $700 due 9 months from today are to be replaced by a $1,100 payment 6 months fro today and another payment 21 months from today. If money is worth 2.9% compounded quarterly, find the amount of the unknown payment. Determine the economically equivalent value for each payment amount at the appropriate focal date by entering the remaining values in the blanks below: Round all dollar values to two decimal places. For the $1,000 due today: N = 7 (10 %) PV = 1000 (10 %) FV = 1051.87 (10 %) For the $700 due in 9 months from today: N = X (X^4$7) PV = x (/^\-?\$?700/) FV = 700 * (/^\-?\$?720\.5/) For the $1,100 due 6 months from today: N = * (/^5$/) PV = * (/^|-?\$?1\,?1007) FV = 1100 * (/^|-?\$?1\,?140\.47) The amount of the unknown payment at the focal date is = * (A^-?\$?631\.97) View Feedback