Mary's $25$th birthday is today, and she hopes to retire on her $65$th birthday. She has determined that she will need to have $$1,000,000$ in her retirement savings account in order to live comfortably. Mary currently has no retirement savings, and her investments will earn $6\%$ annually. How much must she deposit into her account at the end of each of the next $40$ years to meet her retirement savings goal?