The table given below represents the production and sales of wheat in 4 different countries A, B, C and D over a period of 4 years. At the end of year 2010 A, B, C and D had a stock of 5200, 3500, 7835 and 1956 (in '000 quintals) of wheat respectively. For any given year, the stock of wheat is calculated as: Stock of year (n + 1) = stock at end of year (n) + production in year (n + 1) — sales in year (n + 1) And, Surplus of year (n) = production in year (n) — sales in year (n)