An increasing perpetuity begins 3 years from now. The first payment is 10 and increases by 5 each year until 115 is reached. This perpetuity is purchased by 3 annual premiums, with the first premium of X due immediately. Each premium after the first is 106% of the preceding one. The annual interest is 5% during the first 2 years then 6% after. Find X.

Can you show this in formulas, not excel?