(4) Let us mark the vertices on thegiven figure as
There are 18 rectangles in thegiven figure as follows:
(i) MNUT, (ii) TUSV, (iii) SVOP, (iv)MNVS, (v) TUOP, (vi) MNOP, (vii)LTSK, (viii) UIJV, (ix) LUVK, (x) TIJS,(xi) LIJK, (xii) IQRJ, (xiii) EMPH, (xiv)NFGO, (xv) ENOH, (xvi) MFGP, (xvii)EFGH and (xviii) ABDC