What is the total quantity that Cindy Stewart order "Lexmark X 9575 Professional All-in-One Color Printer" in the south superstore?
Lexmark X 9575 Professional All-in-One Color Printer' is the "Product Name"
SELECT SUM(T1.Quantity) FROM south_superstore AS T1 INNER JOIN people AS T2 ON T1.`Customer ID` = T2.`Customer ID` INNER JOIN product AS T3 ON T3.`Product ID` = T1.`Product ID` WHERE T2.`Customer Name` = 'Cindy Stewart' AND T3.`Product Name` = 'Lexmark X 9575 Professional All-in-One Color Printer'