$(/4$ Marks$)$ Consider to relational instances $r(R)$ and $s(S)$ of the schemas $R$ and $S$ respectively, where $R$ and $S$ have the same arity and have compatible domains.

a$.$ Write the logically equivalent statement for $r$ s using only fundamental$/$core relational algebra operations $(2$ marks$),$ but you must use a different relational algebra expression than the one given in lecture: $).$ Hint: explain your solution using a Venn diagram.

b$.$ Explain in clear English the logic behind your relational algebra expression, that is what is each major "chunk" of relational algebra doing, as well as how they are combined $(2$ marks$).$ Hint: use Venn diagrams.