Sandhill Corporation owns machinery that cost $30,000 when purchased on July 1, 2017. Depreciation has been recorded at a rate of $3,600 per year, resulting in a balance in accumulated depreciation of $12,600 at December 31, 2020. The machinery is sold on September 1, 2021, for $7,800. Prepare journal entries to (a) update depreciation for 2021 and (b) record the sale.