What are the quantifiers (marked as “?”) in the following tu…

What are the quantifiers (marked as “?”) in the following tuple relational calculus query: List of project numbers that involve an employee whose last name is ‘Wong’,  as manager of the controlling department for the project. ans :=    { P.pNumber | projects(P) and    ((? M) (? D)      (employee(M) and department(D) and P.dNumber = D.dNumber and D.mgrSSN = M.eSSN and M.lName = ‘Wong’ ) ) };