***** Profit on cost = 33 1/3 %.
Cost = 1/3rd
Profit on sales = 1/4th
And, Sales = Cash Sales + Credit Sales = 60,000+40,000 = Rs.1,00,000
So, Profit = 1,00,000 x 1/4 = Rs.25,000
Cost of Goods Sold = Sales – ***** Profit = 1,00,000 – 25,000 = Rs.75,000
Cost of Goods Sold = Opening Stock + Purchases – Closing Stock
75,000 = 20,000 + 70,000 – Closing Stock
Closing Stock = Rs.15,000