A. Given the following database schema E- Employee (Ename, SSN, Age, salary, Supervisor SSN, Dno) D- Department (Dname, Dnumber, Dlocation Manager. SSN, Mgr. StartingDate) P- Project (Pname, Pnumber Plocation) W-Works On (ESSN, Pno, Hours) De-Dependent (ESSN, D name, DOB, Relationship) and the following set of foreign keys: Employee.Supervisor SSN Employee.SSN Employee.Dno Department.Dnumber Department Manager SSN Employee.SSN Works ON.ESSN Employee.SSN Works On.Pno Proiect.Pnumber Dependent.ESSN Employee.SSN Write the following queries in relational algebra: a. Return the names of those who have the lowest salary in the Employee table; b. Find the names of employees whose salary is higher than that of his/her supervisor; c. Find the names and SSNs of employees who worked on EVERY project located in Brooklyn; d. Find the names of those who worked on exactly two projects