1. A fund of $18,000 is accumulated by means of a number of regular annual deposits of $600 made at the end of every year for as long as necessary, plus a final irregular payment to be made at the end. If the fund earns an effective rate of interest of 9%. Find: a) how many regular deposits will be necessary? b) the amount of the irregular payment to be deposited on the date of the last regular payment? c) the amount of the irregular payment to be deposited one year after last regular payment? d) the amount of the irregular payment be deposited continuously during the year following the last regular payment