For each of the following arguments, inferring just two statements from the premises will produce a formal proof of its validity. Construct a formal proof for each of these arguments.
In these formal proofs, and in all the proofs to follow in later sections, note to the right of each inferred statement the rule of inference that is used to infer that statement. It is most convenient if the justification specifies first the number of the line (or lines) being used, and then the name (abbreviated) of the rule of inference that has been applied to those numbered lines.

(P₁): W ⊃ X
(P₂): ~ Y ⊃ ~ X
∴ W ⊃ Y