What is the correct entry to record the cost of the sale of 2 electric guitars sold to a customer at $550 per guitar including GST?

Under the periodic inventory system, what is the correct entry to record the cost of the sale of 2 electric guitars sold to a customer at $550 per guitar including GST? (The guitars were originally purchased on credit at $250 each plus GST of $25 per guitar.)

A)Debit purchases $1100; credit sales $1100
B)Debit purchases $500; credit inventory $500
C)Debit cost of sales $500; credit inventory $500
D)The cost of each sale is not recorded under the periodic inventory system