SPG Ltd enters into an agreement to sell a machine for $80,000 on 1 June 2021. The machine is delivered on 30 June 2021 and the customer pays in full on 10 July 2021. The sales contract states that SPG Ltd must provide maintenance for the machine for the first 12 months. The customer is entitled to a refund of 20% of the amount paid if SPG Ltd does not satisfactorily service the machine for the year as required. Required: Prepare any journal entries to be recorded for the financial year ended on 30 June 2021 by SPG Ltd as per the recognition criteria in AASB 15. Provide reasons for your entries