sort the list of instances by date, least recent (i. e. oldest) to most recent (i. e. youngest). For example, an instance with the date "2012-10-12" would have a lower index than one with "2012-10-23" and the patent with the date "2010-09-01" would have a lower index than one with "2010-10-11". Assign that list to the variable ordered_dates. Assign to the variable most_recent_patent the case number of the most recent patent. Assign to the variable oldest_patent the case number of the least recent patent.