WASHINGTON (WLMI) Gas prices in the U.S. rose over six-and-a-half cents a gallon during the last two weeks.  The latest Lundberg Survey released yesterday shows the average national price for a gallon of regular unleaded was three-dollars-57-cents on Friday.  However the increase was much less than the 33-cent increase in the prior two-week period.  Trilby Lundberg says oil prices declined somewhat after the earthquake, tsunami and nuclear crisis in Japan.  Lundberg expects another upward trend because of the military action in Libya.  The current average price of gas is about 75-cents higher than a year ago.