Surfs Up P/L is a national retailer that sells a range of surfing and water sport equipment (surfboards, clothing, etc.) with an annual turnover of $60 million. Surfs Up purchases Billapro surfboards for $440 each from Billapong P/L, a large manufacturer of surfboards located at Gold Coast with an annual turnover of around $45 million, this was their only sale for the month. Surfs Up plans to sell the Surfboards at a 200% mark-up to its customers. In October last year it purchased 370 surfboards but a couple of months later (December) they discovered that 14 of the surfboards were faulty and subsequently returned these faulty surfboards to the manufacturer, obtaining a full refund. Assume both apply the accrual method of accounting. Requirement: Explain the GST consequences of this arrangement for both companies.