You are given a perpetuity with annual payments as follows:

payments of $5$ at the end of each of the first $10$ years

payments of $10$ at the end of each of the next $10$ years

payments of $20$ at the end of years $21,22,23,...($continuing in perpetuity$)$

If the effective rate of discount is $5\%,$ find the present value of this perpetuity.