jermaine a retired single taxpayer began receiving a monthly pension from his former employer qualified plan in january 2019.he is 66yrs old when he the first payment,and the pension will pay over the course of his life.he received a form 1099-r for the tax yr. showing a gross distribution of 18,000 in box 1 a code 7 in box 7 and total employee contribution of 20,000 in box 9b. box 2a is blank and box 2b indicates that taxable amt.is not determined , how much of his distrubition is taxable?