determine whether the given argument is valid or invalid. If it is invalid, select a counterexample.
-1. (∃x)(Px • Qx)
2) (∃x)(Px • Rx)
3) (∀x)(Qx ⊃ Sx)
4) (∀x)(Rx ⊃ Tx) / (∃x)(Px • Sx) • (∃x)(Px • Tx)
A) Valid
B) Invalid. Counterexample in a domain of 1 member, in which:
Pa: True Qa: True Ra: True Sa: True Ta: True
C) Invalid. Counterexample in a domain of 1 member, in which:
Pa: False Qa: True Ra: True Sa: True Ta: True
D) Invalid. Counterexample in a domain of 1 member, in which:
Pa: True Qa: True Ra: False Sa: True Ta: True
E) Invalid. Counterexample in a domain of 1 member, in which:
Pa: True Qa: True Ra: True Sa: False Ta: True

Question

Quizplus · Accepted Answer

The argument is valid because from the premises, it logically follows that there exists at least one x such that Px and Sx are true (due to the first and third premises), and there exists at least one x such that Px and Tx are true (due to the second and fourth premises).

Determine Whether the Given Argument Is Valid or Invalid