18. A Company, which closes its books on 31st March every year, purcha on 1st July, 2017, machinery costing 30,000. It purchased further machinery on January, 2018, costing 20,000 and on 1st October, 2018, costing 10,000. On April, 2019, one-third of the machinery installed on 1st July, 2017, became obsole and was sold for 3,000. of the Compa