Cost of assets: $100,000 (Purchased and started to use on 1 January 2018) Estimated Useful life: 4 years Estimated Total Units of activity: 10,000 units Estimated Salvage value: $ 12,000 Units of Production in Year 1: 2000 units The company is adopting straight line method for calculation of depreciation. In the year of purchase or disposal, depreciation is calculated on monthly basis. Sold with sales proceeds on 30 Jun 2020: $53,000 Gain on Disposal = $