Bill and Cathy will be retiring in fifteen years and would like to buy an Italian villa. The villa costs $500,000 today, and housing prices in Italy are expected to increase by 5.5% per year. Bill and Cathy wants to deposit an equal amount at the end of every year so that they can buy this villa in 15 years. If their account earns 7.5% per year, what is the amount of each deposit?