Table schema:
CREATE TABLE table_name_2 (frequency INTEGER, callsign VARCHAR, webcast VARCHAR, city_of_license VARCHAR)

Question: Which long range AM station has the lowest frequency and includes a webcast of listen live, was licensed in the city of Monterrey, and uses the Callsign of xet?
SQL: SELECT MIN(frequency) FROM table_name_2 WHERE webcast = "listen live" AND city_of_license = "monterrey" AND callsign = "xet"