Write SQL query to solve given problem: Among the cars on a train that runs in the east direction, how many of them have a flat roof and a circle load shape?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT SUM(CASE WHEN T1.load_shape = 'circle' THEN 1 ELSE 0 END)as count FROM cars AS T1 INNER JOIN trains AS T2 ON T1.train_id = T2.id WHERE T2.direction = 'east' AND T1.roof = 'flat' 