Two triangles △PQR and △PQR′ share the same base PQ with P(1,1) and Q(5,1). Their third vertices are R(3,7) and R′(3,9) respectively.
(i) Compute the area of △PQR.
(ii) Compute the area of △PQR′.
(iii) Compare the two areas and express the ratio area(△PQR′)area(△PQR).