Question: what is the platform when the frequency (per hour) is 4 and the destination is West Croydon?
SQL: SELECT SUM("Platform") FROM "2-1132489-1" WHERE "Frequency (per hour)" = 4.0 AND "Destination" = 'West Croydon';

Question: what is the highest platform number when the frequency (per hour) is 4, the operator is London Overground and the destination is West Croydon?
SQL: SELECT MAX("Platform") FROM "2-1132489-1" WHERE "Frequency (per hour)" = 4.0 AND "Operator" = 'London Overground' AND "Destination" = 'West Croydon';