4. For each separate part give a careful proof of the target equation (state a sequence of equalities for the left-hand side, ending up with the right-hand side, and next to each equal thing you write down, state which axioms and/or theorems you are using. It is recommended that you not "skip steps"). a. [2 points) AC+B + AC + AB =+B b. 3 points) ABC +C = BC +C c. [3 points) A+ AC + BC + ABC = A + BC