Four matrices P, Q, R and S have respective orders x×y, y×z, z×t and t×x, where x,y,z,t are positive integers.
(i) Show that the product PQRS is defined and determine its order.
(ii) Prove that PQRS is always a square matrix, whatever positive integer values x,y,z,t may take.
(iii) Derive an expression, in terms of x, for the total number of elements contained in PQRS.
(iv) Verify your result in part (iii) for the specific choice x=4,y=2,z=5,t=4.