4. (20 points) Queries Consider the following sche ma of an administrative database for college personnel: PROFESSOR(SSN, FNAME, LNAME, RANK, SALARY) DEPARTMENT(NAME, OFFICE, PHONE, CHAIRID) MEMBER(DEPT NAME, PROF ID Primary keys are underlined in the schema definition. Foreign keys are as follow: field in schema references schema CHAIRID DEPARTMENT SSN of PROFESSOR PROF ID MEMBER SSN of PROFESSOR DEPT NAME MEMBER NAME of DEPARTMENT Write the following queries in Relational Algebra. (a) Retrieve full name (first and last) and rank of each professor who earns more than 40000 dol salary