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 Project.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