For a library, the entity type HOLDING has four subtypes: BOOK, AUDIO BOOK, DVD, and SOFTWARE. Draw a separate EER diagram segment for each of the following situations: a. At a given time, a holding must be at least one of these subtypes. b. At a given time, a holding must be exactly one of these subtypes. c. A holding may or may not be one of these subtypes. On the other hand, a holding may be any two (or even four) of these subtypes at the same time. d. A holding may or may not be one of these subtypes. However, a holding that is one of these subtypes can- not at the same time be one of the other subtypes.