Write SQL query to solve given problem: How many stores with less need for products, and purchased through a distributor, are located in Washtenaw County?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT SUM(CASE WHEN T1.`Order Quantity` = 1 AND T1.`Sales Channel` = 'Distributor' AND T2.County = 'Washtenaw County' THEN 1 ELSE 0 END) FROM `Sales Orders` AS T1 INNER JOIN `Store Locations` AS T2 ON T2.StoreID = T1._StoreID