question: Name the average ERP W when it has a city of license of pound, virginia and frequency mhz more than 91.3
answer: SELECT AVG(erp_w) FROM table_name_90 WHERE city_of_license = "pound, virginia" AND frequency_mhz > 91.3
context: CREATE TABLE table_name_90 (erp_w INTEGER, city_of_license VARCHAR, frequency_mhz VARCHAR)