2. [15 Points] Consider an E/R diagram which includes the entity sets F={c,d},G={e}, and H={g,h}; the key attributes are underlined. The diagram also includes a relationship S={f} between G and H, with f as its own attribute. There is also a weak entity set E={a,b} to which G is connected via an "isa" relationship. Finally, there is a many-to-one weak relationship R from E to F with a rounded arrow entering F. Convert this diagram into a relational database schema using the following approaches, and in each case show the relations obtained and underline the key attributes. (a) the E/R style (b) the OO approach (c) the null approach