Sea ice in the Arctic ocean increases and decreases annually. Declines have even made it possible for shipping to occur through the "Northwest Passage" in recent summer seasons. The following data, shown in Table 8.10, were obtained from the NASA Earth Observatory website and represent the maximum and minimum sea ice extent, measured in September (minimum) and March (maximum) of the following year. The first line in the table is the average for the previous 20 years. (a) Plot both the September values and March values vs. the year, and add a line representing the average ice extent for 1979-2000. (b) Use the 1979-2000. (c) Use the find command to determine which years were lower than the average February values for 1979-2000. (d) Since the extent of Arctic sea ice has continually decreased from the previous 20 year average, a more interesting calculation would be to find the average sea ice extent over the years from 1999 to 2012. Repeat parts (b) and (c) using this new average. find command to determine which years exceeded the average September values for