Sammy owns a hat shop.

During the 2020 financial year, Sammy bought 30 hats at a cost of $110 each which she sold throughout the year for $330 each. She also bought 5 hats for $88 each and sold three (3) of these hats for $220 each.

Calculate how much GST Sammy owes for the 2020 tax year. Show all calculations and explain your answer.