Draw a complete EERD for the following situation. There are graduate students at a university. Some are employed by the university as teaching associates (TAs); some are employed as research associates (RAs); some are not employed by the university at all. For the TAs, we need to know the course assignment; for the RAs, we need to know the research grant to which they are assigned. Students cannot be both a TA and a RA at the same time.