Under the perpetual inventory system, three office desks were originally purchased on CR at $300 each plus 10% GST. If all three desks were sold to a customer at $550 each (including GST) what is the correct entry to record the cost of the sale? DR Cost of sales $1650; CR Sales $1650. DR Cost of sales $900; CR Sales $900 DR Cost of sales $900; CR Inventory $900. DR Cost of sales $900; DR GST receivable $90; CR Inventory $990