With reference to the cost data given, analyse the unit rates for external wall in the Bills of Quantities below. ITEM DESCRIPTION UNIT QTY RATE AMOUNT A B EXTERNAL WALLS Non-loadbearing superstructure Common clay bricks, in cement and sand mortar (1:3) with brick reinforcement at every forth course One brickwork in English bond Half brickwork in Stretcher bond m2 m2 2,190 1,632