question is clear

3. For each of the following pairs of types. say whether they can be unified or not. If they can be unified, list the substitutions for type variables that need to he made to achieve this. You are not allowed to rename apart the occurrences of type variables. Be careful not to create infinite types (for example, 'a and 'a list cannot be unified). E.g., the pairs 'a list * 'b and 'c * (int -> 'c) unify, and this achieved by taking ?c> ?a list and 'b int -> 'a list. The pairs 'a -> int and bool -> 'a do not unify. }}-}'}_11 (i) 'a -> ?aand 'a -> int list (Using FH) Gi) ?a -> ?band 'a -> int list Gil) (int -> int) -> (int -> int) and'a -> 'a Gv) ?a list -> 'a list and 'b -> 'b (v) ?a list -> 'aand 'b -> 'b (vi) (?a -> ?b) -> ?cand 'd -> 'e list 3. For each of the following pairs of types. say whether they can be unified or not. If they can be unified, list the substitutions for type variables that need to he made to achieve this. You are not allowed to rename apart the occurrences of type variables. Be careful not to create infinite types (for example, 'a and 'a list cannot be unified). E.g., the pairs 'a list * 'b and 'c * (int -> 'c) unify, and this achieved by taking ?c> ?a list and 'b int -> 'a list. The pairs 'a -> int and bool -> 'a do not unify. }}-}'}_11 (i) 'a -> ?aand 'a -> int list (Using FH) Gi) ?a -> ?band 'a -> int list Gil) (int -> int) -> (int -> int) and'a -> 'a Gv) ?a list -> 'a list and 'b -> 'b (v) ?a list -> 'aand 'b -> 'b (vi) (?a -> ?b) -> ?cand 'd -> 'e list