The grammar G₂ is ambiguous. Give a string having two different parse trees in G₂. For each of these parse trees, write down a derivation for the string.

Suppose we adopt the following disambiguating rule used in most languages: match each else with the closest previous unmatched then.

Using this disambiguating rule, write an unambiguous grammar that is equivalent to grammar G₂.

Consider the following BNF grammar G2 used in the next two questions if expr then | other expr : := true | false where other is a terminal that stands for any other kinds of statements, and is the start non-terminal