1. ~M•(Z > R) 2. (~M v G) > ~U 3. (~M v ~X) > ~B 4. (~B • ~U ) > (E > M) / ~E 5. ~M 1, simplification 6. ~M v G 5, addition 7. ~U 2,6, modus ponens 8. ~M v ~X 5, addition 9. ~B 3,8, modus ponens 10. ~B • ~U 9,7, conjunction 11. E > M 4,10, modus ponens 12. ~E 11,5, modus tollens Edwin