Relational Calculus


#1

*****Please explain why option IV is not correct *****

Which of the following tuple relational calculus expression(s) is/are equivalent to ∀t∈r(P(t))∀t∈r(P(t))?

I. ¬∃t∈r(P(t))¬∃t∈r(P(t))
II. ∃t∉r(P(t))∃t∉r(P(t))
III. ¬∃t∈r(¬P(t))¬∃t∈r(¬P(t))
IV. ∃t∉r(¬P(t))∃t∉r(¬P(t))

I only
II only
III only
III and IV only

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