In Silver Bow County, Montana, when the capicity is more than 45 tons, what's the highest rank found?
CREATE TABLE "leading_copper_producing_mines" (
  "rank" real,
  "mine" text,
  "county_and_state" text,
  "operator" text,
  "source_of_copper" text,
  "capacity_thousands_of_metric_tons" real
);
SELECT MAX("rank") FROM "leading_copper_producing_mines" WHERE "county_and_state"='silver bow county, montana' AND "capacity_thousands_of_metric_tons">45;