I.   Complete the derivation from the lesson.

      II.   Complete the following derivations:

           A.   Derive Q v S from

               1.   P -> (Q v S)            Premise
               2.   ~Q -> P                 Premise
               3.   Q -> R                  Premise
               4.    ~R v T                 Premise
               5.   ~T                      Premise

           B.   Derive Q v S from

               1.   P v (T v R)             Premise
               2.   U -> ~P                 Premise
               3.   (T -> Q) & (R -> S)     Premise
               4.   W & (U & V)             Premise