$(/5$ marks$)$ Using the university example, write relational$-$algebra queries to find the sections taught by more than one instructor in the following ways: Hint: we want find the sections for a given $($course$,$ year, semester$)$ that is taught by more than one instructor. Be sure to include al the attributes required to uniquely identify the section..

a$.$ Using an aggregate function $(2$ marks$).$

b$.$ Without using any aggregate functions $(3$ marks$).$ Hint: you need to compare the relation to itself, but make sure the sections you compare are equal for the right attributes and don't compare sections from different years of semesters.