relational algebra specific operations <p>I have these tables</p> <pre><code>Employee(ssn, name, sex, address, salary, bdate, dno, superssn) fk:superssn is ssn in Employee fk:dno is dnumber in Department Department(dnumber, dname, mgrssn, mgrstartdate) fk:mgrssn is ssn in Employee Dept_locations(dnumber, dlocation) fk:dnumber is dnumber in Department Project(pnumber, pname, plocation, dnum) fk:dnum is dnumber in Department Dependent(essn, dependent_name, sex, bdate, relationship) fk: essn is ssn in Employee Works_on(essn,pno,hours) fk: essn is ssn in Employee; pno is pnumber in Project </code></pre> <p>I would like to retrieve the list of locations for the finance department using only the following relational algebra operations {σ, π, ∪, ρ, −, ×}.</p> <p>so far i have: π dlocation (σ department (dname = 'research'))</p> <p>i'm really stuck, and confused... i don't know if its possible to do it without an equijoin operation.</p>