Database systems

2.) (5 POINTS) Consider the following relational database. Specify the probable primary key (PK) for each relation. Justify the reason why you decide that way. Staff (staffLastName, streetNo, street, city, zip) WorksAt (staffLastName, branchName, hourlyPaid, monthlyPaid, salary) Branch (branchName, city) 3. (20 POINTS) Assume following two relations belong to a campus database: student(sid, fname, lname, major, totalCredit) enrolled sid, cid, sectionID, semester, year, grade) What is the corresponding English statement for the following relational algebra expressions? 3.A.) (10 POINTS) Gyear 2016 (enrolled student) 3.B.) (10 POINTS) ? sid, cid, fname, lname (student p enrolled)