The Continental Bank made a loan of $23,000.00 on March 4 to Dr. Hirsch to purchase equipment for her office. The loan was secured by a demand loan subject to a variable rate of interest that was 5% on March 4 . The rate of interest was raised to 5.3% effective July 1 and to 5.8% effective September 1 . Dr. Hirsch made partial payments on the loan as follows: $900 on May 25; $700 on June 29; and $200 on October 22 . Each payment is first applied to any accumulated interest. Any remainder is then used to reduce the outstanding principal. The terms of the note require payment on October 31 of any interest not paid off by partial payments. How much must Dr. Hirsch pay on October 31