Table: rail_info
Columns: line
began_operation
stations
length_km
terminals

Question: When is the earliest began operation with a length of sultan ismail and over 27 stations?
SQL: SELECT MIN("began_operation") FROM rail_info WHERE "length_km" = 'sultan ismail' AND "stations" > 27

Question: What is the average operation beginning with a length of ampang and over 27 stations?
SQL: SELECT AVG("began_operation") FROM rail_info WHERE "length_km" = 'ampang' AND "stations" > 27