What is the impact on the money supply of a reduction in the required reserve ratio?
Theoretically, reducing the required reserve ratio will increase the money supply by allowing banks to produce more loans and keep less in reserve.  Theoretically your simple (ie basic homework) calculation would show that the money supply could increase by that amount.  In practice there are of course many other factors, such as the interest rate, velocity and reliablility of the people taking out the loans.