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3.21 Simplify each of the following expressions using only the consensus theorem (or its dual): (a) BCD+ABC+ACD+ABD+ABD (reduce to three terms) (b) WY+WYZ+XYZ+WXY (reduce to three terms) (c) (B+C+D)(A+B+C)(A+C+D)(B+C+D) (d) WXY+WXZ+WYZ+WZY (e) ABC+BCD+ACD+BCD+ABD (f) (A+B+C)(B+C+D)(A+B+D)(A+B+D)