For the period from 2016 through 2016, the Charlie Company had net sales of $500,000 and a gross profit of $200,000. During the first quarter of 2018 the company made a purchase of $19,500 and recorded sales of $47,500. The inventory value at the beginning of the year was 15,500. What is the estimated cost of Charlie's inventory on March 31, 2018 using the gross profit method?