explanation needed

A trader prepared his accounts on 31st March, each year. Due to some unavoidable reasons, no inventory taking could be possible till 15th April , 2017 on which date the total cost of goods in his godown came to ? 5,00,000. The following facts were established between 31st March and 15th April, 2017. () Sales ? 4,10,000 (including cash sales 1,00,000) (i) Purchases 50,340 (including cash purchases 19,900) (ii) Sales Return 10,000. Goods are sold by the trader at a profit of 20% on sales. You are required to ascertain the value of inventory as on 31st March, 2017