Use the rules of inference to prove that the following argument is valid. At each step, include the name of the rule used and from which "letter" each premise comes from.

a$.PQ$

b$.$ notX

c$.T$not$(RorS)$

d$.T$ and $U$

e$.WorY$

f$.Y$X

g$.Q(RorS)$

therefore notQ and $W$