user: Question:  what's the engine where builder is Gloucester RCW and withdrawn is 1959
Columns: ['Number Range', 'Introduced', 'Builder', 'Engine', 'Weight (long tons)', 'Seats', 'Withdrawn', 'Notes']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['1', '1934', 'Park Royal', '1 AEC of hp (kW)', 'long tons (t; short tons)', '69', '1955', 'Prototype railcar']
SQL:

assistant: SELECT "Engine" FROM "Table" WHERE "Builder" = 'Gloucester RCW' AND "Withdrawn" = '1959';