The benefits arising from the construction of a dam to provide irrigation water are estimated as follows:

In the first five years after completion $100,000 per year; in the next five years $200,000 per year; in the next fifteen years $300,000 per year; in the next 50 years $400,000 per year.

- What is the present worth of these benefits at completion date if the interest rate is 5% per annum?