Determine Whether the Given Argument Is Valid or Invalid

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

Correct Answer:

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