Jim purchases machine A$1$ on $1$ January $2019$ for $$20000.$ On $1$ April $2020$ a second machine A$2$ costing $$30000$ is purchased paying by cheque. On $1$ September $2021,$ the first machine A$1$ is being disposed and sold at $$17000$ and on the same date another machine A$3$ is bought on credit from XYZ Ltd for $$40000$ to replace the one disposed. Depreciation is calculated at the rate of $10\%$ per annum on the diminishing balance method. A full year$$s depreciation is charged in the year of purchase but none in the year of sale.