Write SQL query to solve given problem: How many orders in the south superstore with the fastest delivery are items of furniture?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT COUNT(T1.`Order ID`) FROM south_superstore AS T1 INNER JOIN product AS T2 ON T1.`Product ID` = T2.`Product ID` WHERE T1.`Ship Mode` = 'First Class' AND T2.Category = 'Furniture'