[['class', 'introduced', 'number in class', 'number in service', 'power output (kw)'], ['dbr', '1980', '10', '7', '709'], ['dc', '1978 - 1981', '85', '69', '1230'], ['dft', '1979 - 1981', '30', '29', '1800'], ['dh', '1979', '6', '6', '672'], ['dl', '2010 -', '48', '40', '2700'], ['dsc', '1959 - 1967', '70', '44', '315'], ['dsg', '1981', '24', '24', '700'], ['dsj', '1982', '5', '5', '350'], ['dx', '1972 - 1975', '49', '46', '2240'], ['dxr', '1993', '2', '2', '2420'], ['ef', '1988 - 1989', '22', '17', '3000'], ['tr', '1936 - 1978', '90', '21', '138']]
the Tr Class is the 1 that was Introduced at the earliest date
the [ENT] [ENT] is the 1 that was [ENT] at the earliest date