CREATE TABLE table_name_21 (frequency_mhz INTEGER, city_of_license VARCHAR(255), erp_w VARCHAR(255))
In Los Banos, California, when the ERP W is than 10, what is the average Frequency MHz?
    
SQL: SELECT AVG(frequency_mhz) FROM table_name_21 WHERE city_of_license = "los banos, california" AND erp_w < 10