1. Develop histogram. The function consumes a list of grades between 0 and 100; it produces a vector of size 101 where each slot contains the number of grades at that level.
2. Develop count-children. The function consumes a descendant family tree, which is a family tree that leads from a family member to the descendants. It produces a vector with six fields. The first five slots contain the number of family members that have that many children; the sixth field contains the number of family members that have five or more children.