University Bookstore ordered 500 copies of an introductory economics text book from the publisher on July 17,2007. The books were delivered on August 12, at which time a bill was sent requesting payment of 40 Be. Per book. However , a 2% discount was allowed if the publisher received payment on September 12. University Bookstore sent the proper payment which was received by the publisher on September 10. University Bookstore returned 60 books to the publisher for a full Cash refund. Prepare the journal entries ( if any ) for the publisher on: a) July 17 b) August 12 c) September 10 d)December 18.