Im having trouble figuring this question out.

Barnes Bank lent $20,000 to the owner of an established restaurant for some muchneeded renovations.This demand loan was given on February 1, 2012 at 7.5% p.a.simple interest.Partial payments were made of $1000on June 10, $400 onSeptember 20, and $1200 on November 15.

Using the declining balance method, calculate the outstanding balance on December 31.