4. Express (i) $23 \cdot 53$, (ii) $43 \cdot 197$, (iii) $47 \cdot 223$ as the sum of four squares in two different ways.
4. (i) $23 \cdot 53=27^{2}+15^{2}+12^{2}+11^{2}=25^{2}+19^{2}+13^{2}+8^{2}$;
(ii) $43 \cdot 197=74^{2}+51^{2}+15^{2}+13^{2}=69^{2}+57^{2}+19^{2}+10^{2}$;
(iii) $47 \cdot 223=101^{2}+12^{2}+10^{2}+6^{2}=77^{2}+54^{2}+40^{2}+6^{2}$.