Construct a BNF for each of the following languages. Is your grammar ambiguous? If yes, rewrite it to be non-ambiguous. Give an input string of the language and draw the parse tree and AST for your input.

1. a sequence of variable declarations separated by ;, each declaration in the format of val x : t = e, where val is a keyword, x is an arbitrary identifier (variable name), t is either int or float, and e is an arbitrary expression as described. The following shows an example input that should be derived by your BNF. val x1 : int = 5; val y : float = 0.; val z : int = x * 2