Let AMBIGCFG = {hGi| G is an ambiguous CFG}. Show that

Let AMBIGCFG = {hGi| G is an ambiguous CFG}. Show that AMBIGCFG is undecidable. (Hint: Use a reduction from PCP. Given an instance P =ht1 b1i, ht2 b2i, ... ,htk bki of the Post Correspondence Problem, construct a CFG G with the rulesS T | B T t1Ta1 | | tkTak | t1a1 | | tkak B b1Ba1 | | bkBak | b1a1 | | bkak ,where a1,...,ak are new terminal symbols. Prove that this reduction works.)