SCHEMA:
CREATE TABLE table_name_21 (rank INTEGER, county_and_state VARCHAR, capacity__thousands_of_metric_tons_ VARCHAR)
USER:
In Silver Bow County, Montana, when the capicity is more than 45 tons, what's the highest rank found?

QUERY:
SELECT MAX(rank) FROM table_name_21 WHERE county_and_state = "silver bow county, montana" AND capacity__thousands_of_metric_tons_ > 45