Fig. 4.6 shows an archway which is a segment of a circle with centre O and diameter 4 m. M is the midpoint of AB and LM is perpendicular to AB. A Fig. 4.6 a If IOMI = IAMI = IMBI, calculate |AB| correct to 2 decimal places. Fig. 4. a Sh in b F (12) b Calculate, correct to 3 significant figures, the perimeter ALB of the archway. (Take [WAEC] to be 22/7 or 3.142.)​