Consider this query: Retrieve the SSNs of employees who work on at least those projects on which the employee with SSN = 123456789 works. This may be stated as (FORALL x) (IF P THEN Q), where
• x is a tuple variable that ranges over the PROJECT relation.
• P M employee with SSN = 123456789 works on project x.
• Q M employee e works on project x.
Express the query in tuple relational calculus, using the rules
• ( x)(P(x)) M not( x)(not(P(x))).
• (IF P THEN Q) M (not(P) or Q).