A person is considering entering into an agreement with an investment company to deposit $1000 into a special account at the end of the first year, $1100 second year, and increasing by $100 every year for 15 years. At the end of 15 years, the person would be able to withdraw $36000. At which rate does the person earn interest if the interest is compounded annually?

The answer is 5.54% per year. I am trying to understand why.