Draw an ER diagram for each of the following situations. On the diagram be sure to identify the cardinality, existence, and optionality (for subtypes) of each relationship.

1. A university has a large number of courses in its catalog. Each course may have one or more other courses as prerequisites, or may have no prerequisites.

2. A video store may stock more than one copy of a given movie. It is also true that the store may not have a single copy of a particular movie.