Which trip id had the longest duration and the start station is in Redwood City?
longest duration refers to MAX(duration); start station refers to start_station_name;
SELECT T1.id FROM trip AS T1 LEFT JOIN station AS T2 ON T2.name = T1.start_station_name WHERE T2.city = 'Redwood City' AND T1.duration = ( SELECT MAX(T1.duration) FROM trip AS T1 LEFT JOIN station AS T2 ON T2.name = T1.start_station_name WHERE T2.city = 'Redwood City' )