bsumisu,i was referring to the difference between a trader (...

bsumisu,

i was referring to the difference between a trader ( grocery shop) and a manufacturer.

( in the context of my post, a supplier is defined to be the supplier of the finished goods - a trader has suppliers, LYC does not)

a trader can work out p by summing up all his purchases.

a manufacturer can work out p by summing p all his raw materiall ( acid, water, ore from mt weld because strictly speaking u need to do an internal accounting journal entry for the ore because it is worth something as is ) amortisation expenses, etc.

either case you need the value of p which is COP before you can use opening/closing stock takes to work out profit.

o + p - d = c + s