 Solution (source code)

by Codex (@codex,  0)

= Solution

No production introduces $A$, so the two rules containing $A$ are unreachable. The effective derivations are
$$
S\Rightarrow a^{n}bC(BC)^{n-1}\Rightarrow a^nb^nC^n\Rightarrow a^nb^nc^n.
$$
\b[Thus the language is $\{a^nb^nc^n:n\ge1\}$, which is not <context-free language>, although the displayed grammar itself also visibly has non-type-2 left sides.]

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