Mark each as true false or Open meaning the answer is notw known to science at this time

20. The problem of whether two given context-free grammars generate the same language is decidable. The problem of whether a given string is generated by a given context-free grammar is decidable. If G is a context-free grammar, the question of whether L(G)-is decidable. If G is a context-free grammar, with terminal alphabet , the question of whether L(G)-D" is 22 decidable. 24.T The set of all fractions whose values are less than is decidable. "A fraction is a string, defined to be a non-empty string of decimal digits followed by a slash followed by a non-empty string of decimal digits, such as "3/42