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Convert an arbitrary CFG into Backus Normal Form CFG S + ASB A AAS|ale B SbS|A|bb Overall steps: How to convert CFG to CNF? Step 1. Eliminate start symbol from RHS. If start symbol S is at the RHS of any production in the grammar, create a new production as: SO->S where SO is the new start symbol. Step 2. Eliminate null, unit and useless productions. If CFG contains null, unit or useless production rules, eliminate them. Step 3. Eliminate terminals from RHS if they exist with other terminals or non-terminals. e.g,; production rule X->xY can be decomposed as: X->ZY Z->x Step 4. Eliminate RHS with more than two non-terminals. e.ge; production rule X->XYZ can be decomposed as: X->PZ P->XY