James Balog's assistants traveled top Ilulissat Glacier in Greenland, which is the most productive glacier in the northern hemisphere (meaning it produces the most ice burgs). They traveled there to watch for a large calving event. After a long wait, they witnessed the largest calving event ever documented. From 1902 to 2001, this glacier retreated ___ miles and from 2000-2010 it retreated ___ miles.