Table schema:
CREATE TABLE table_10408617_5 (prefixes VARCHAR, scheme VARCHAR, approx_premium VARCHAR)

Question: What prefixes are priced at pence per minute, fixed at all times with a premium of 3p/min?
SQL: SELECT prefixes FROM table_10408617_5 WHERE scheme = "Pence per minute, fixed at all times" AND approx_premium = "3p/min"