(c) RhombusCo-ordinates of P are \(\bigg(rac{-1-1}{2},rac{-1+4}{2}\bigg)\)i.e, \(\big(-1,rac{3}{2}\big)\)Co-ordinates of Q are \(\bigg(rac{-1+5}{2},rac{4+4}{2}\bigg)\)i.e, (2, 4)Co-ordinates of R are \(\bigg(rac{5+5}{2},rac{4-1}{2}\bigg)\)i.e, \(\big(5,rac{3}{2}\big)\)Co-ordinates of S are \(\bigg(rac{-1+5}{2},rac{-1-1}{2}\bigg)\)i.e, (2, -1)Now,⇒ PQ = QR = RS = SP ⇒ All sides are equalAlso, PR = \(\sqrt{(5+1)^2+\big(rac{3}{2}-rac{3}{2}\big)^2}\) = \(\sqrt{36}\) = 6SQ = \(\sqrt{(2-2)^2+(4+1)^2}\) = \(\sqrt{25}\) = 5⇒ PR ≠ SQ ⇒ Diagonals are not equal ⇒ PQRS is a rhombus.