user: Question: In which class had 252 laps and a position of DNF?
Columns: ['Year', 'Team', 'Co-Drivers', 'Class', 'Laps', 'Pos.', 'Class Pos.']
Types: ['real', 'text', 'text', 'text', 'real', 'text', 'text']
Sample row: [1996.0, 'West Competition David Price Racing', 'John Nielsen Thomas Bscher', 'GT1', 338.0, '4th', '3rd']
SQL:

assistant: SELECT "Class" FROM "Table" WHERE "Pos." = 'DNF' AND "Laps" = 252.0;