How many products with the highest expected profits were sold in total?
Products refer to productCode; Expected profits = SUBTRACT(MSRP, buyPrice);
SELECT SUM(t2.quantityOrdered) FROM orderdetails AS t2 INNER JOIN ( SELECT t1.productCode FROM products AS t1 ORDER BY t1.MSRP - t1.buyPrice DESC LIMIT 1 ) AS t3 ON t2.productCode = t3.productCode