please do this question with pen and paper using formulas and not in excel

Consider the three 20-year annuities described below: (0) level payments of 1,000 payable annually in arrears (11) increasing payments made annually in arrears, where the first payment is 1,000 and the payments increase by 10% pa compound each year thereafter continuous payments at the rate of 1,000 pa over the 20 years. Calculate the discounted mean term of each annuity using an interest rate of 10% po effective