Consider two triangles △ABC and △DEF.
a. (i) Define the term "included angle" of a pair of sides of a triangle.
b. (ii) It is given that AB=DE, AC=DF and ∠BAC=∠EDF. Are the two triangles necessarily congruent? If yes, name the congruence criterion applied and give a brief reason.
c. (iii) Suppose instead of the equality in part (ii) it is known that ∠ABC=∠DEF while the side equalities remain the same. Does this new set of data guarantee congruence? Give a short justification for your answer.