Hi can you provide detailed explanation for the problem below? I couldn't figure out how the person who answered the question came up with the grammar.

Consider a language of strings that contains only X s, Y s and Z s. A string in this language must begin with an X . If a Y is present in a string, it must be the final character of the string. a. Write a recursive grammar for this language. b. Write all the possible two-character strings of this language.