On October 1, 2011, Sloan Oil Inc. entered into a 6-month, $650,000 purchase commitment for a supply of oil. On December 31, 2011, the market value of oil had fallen to $552,500. Make the journal entries necessary on December 31, 2011, and on March 31, 2012, assuming that the market value of the inventory on March 31 is $430,000.