3. 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?

a. DR Cost of sales $1650; CR Sales $1650

b. DR Cost of sales $900; CR Sales $900

c. DR Cost of sales $900; CR Inventory $900

d. DR Cost of sales $900; DR GST receivable $90; CR Inventory $990

which one is correct?