$9.$ When you retire, you would like to have a monthly pension of $$8,000$ per month for $30$ years. Assume you have just had your $25$th birthday and you intend to contribute monthly to your retirement fund until you are $60.$ The month after that you will start withdrawing your pension. Your investment advisor has found a guaranteed investment for your fund that will yield $8\%$ per year, compounded quarterly for the duration of your pension needs. How much should you contribute each month to your retirement fund, assuming your contributions start one month after your $25$th birthday?