Question: Among the menus in which the dish "Clear green turtle" had appeared, how many of them used the dollar as their currency?
SQL: SELECT SUM(CASE WHEN T3.currency = 'Dollars' THEN 1 ELSE 0 END) FROM MenuItem AS T1 INNER JOIN MenuPage AS T2 ON T1.menu_page_id = T2.id INNER JOIN Menu AS T3 ON T2.menu_id = T3.id INNER JOIN Dish AS T4 ON T1.dish_id = T4.id WHERE T4.name = 'Clear green turtle'