Janet and Denise have both been given $15,000 by their grandparents today on their 21st birthdays. They want to save for their future and have aspirations of one day being millionaires. Each woman plans to make annual contributions on her birthday, beginning next year. Janet and Denise have each opened investment accounts at the 1st National Bank and 2nd National Bank, respectively, and they expect to earn nominal returns of 6% and 7%, respectively. Janet has already decided to deposit $7,500 each year into her investment account, while Denise is unsure of the amount she will deposit annually. How many years will it take Janet before she reaches her investment goal of $1 million?