How to solve it?

4.24. A policy is issued at age 20 with the following graded scale of death benefits payable at the moment of death. Age Death Benefits 20 1 000 21 2 000 22 4 000 23 6 000 24 8 000 25-40 10 000 41 and over 50 000 Calculate the actuarial present value on the basis of the Illustrative Life Table with uniform distribution of deaths over each year of age and i = 0.05. [Hint: A backward recursion formula for the actuarial present value will include a function c(x) that incorporates the death benefit scale.]