What rank is the Silver Bell mine of Pima county?
CREATE TABLE "leading_copper_producing_mines" (
  "rank" text,
  "mine" text,
  "county" text,
  "operator" text,
  "capacity_thousands_of_metric_tons" text
);
SELECT "rank" FROM "leading_copper_producing_mines" WHERE "county"='pima' AND "mine"='silver bell';