Could you please urgently help with the following long term discounting problem?

Question 5: Long Term Discounting (15 points) Assume a project will result in benefits of $50 trillions in 400 years by avoiding an envi ronmental disaster that otherwise would occur at that time. (a) (5 pts) Compute the present value of these benefits using a time-constant discount rate of 2%. (b) (5 pts) Compute the present value of these benefits using the following time-declining discount rate schedule: 4 percent for years 1-50; 3 percent for years, 51-100; 2 percent for years 101-200; 1 percent for years 201-300; and 0 percent thereafter. (c) (5 pts) Compute the present value of these benefits using the following time-declining discount rate schedule: 4 percent for years 1-50; 3 percent for years, 51-100; 2 percent for years 101-200; 1 percent for years 201-300; and 0.5 percent thereafter. Note: Use discrete time interest rates for this exercise (instead of continuous time interest rates), i.e. to discount "X" for a year at an interest rate of 5% we would use PV (X ) - 145% (instead of PV(X) - X . e-5%)