Dennis McDaniel has just started working with the BCN Ltd$.$ as a sales representative and is just trying to catch up on having money for retirement. BCN offers him a pension plan with an annuity that is guaranteed to earn $8\%$ interest compounded annually. He plans to work for $20$ years before retiring and would then like to be able to draw an income of $$500,000$ per month for $15$ years. How much must be deposited per annum into his retirement fund to accomplish this?