Write SQL query to solve given problem: In customers with the first name of Erica, how many of them bought a quantity below 200?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT COUNT(T1.ProductID) FROM Sales AS T1 INNER JOIN Customers AS T2 ON T1.CustomerID = T2.CustomerID WHERE T2.FirstName = 'Erica' AND T1.Quantity < 200