Relational Algebra Query Tree:

                     ∪
                   /   \
                  π     π
                 /       \
               σ         σ
              / \       / \
         Dname  >    Dname  >
            =    30000    =  
           / \      / \   / \
      Employee DNO  Dnumber Pname
              =    =       =
             / \  / \     / \
         SSN Lname  Dnum salary
                          >
                          =
                          / \
                     Project Reorganization
                                  Computerization