Q$3$: Oldham Farms Supply's records for the first three month in $2012$ show purchases of Commodity $AB$ as following

$\backslash$table$[[$Details$,,],[$Jan$.2012,\backslash$table$[[$Number of units$],[5500]],$Costs$],[$Feb$.2012,\backslash$table$[[5,500$ units $5\mathrm{.}45]],29,975$ $ $,5$