## Context free Grammars

Consider the following production rules.

1. S ? A|B|SC|? 2. A?B|D 3. B ? AaB|aCd

4. C ? BBc|A|F 5. D?d|A

Find all variables that cannot be reached from S. You should draw a dependency graph. Find all variables that cannot derive a all-terminal string. Explain the procedure briefly. Find all pairs variables (X, Y ) such that X ?? Y . You should draw a dependency graph.