Using Relational Algebra specify the following queries on the COMPANY relational database schema

(a) For each project, find the total spent hours by all employees

(b) For each project, list the names of projects the have total spent hours (spent by all employees) less than the average spent hours of all projects.

(c) Retrieve the names of employees who work on every project controlled by Research department.

EMPLOYEE Fname Minit Lname Ssn Bdate Address Sex Salary Super_ssn Dno DEPARTMENT Dname Dnumber Mgr ssn Mgr_start date DEPT LOCATIONS Dnumber Dlocation PROJECT PnamePnumber Plocation Dnum WORKS ON Essn Pno | Hours DEPENDENT Essn Dependent name SexBdate Relationship