user: Question: What constructor has a grid less than 21, and time/retired of Engine?
Columns: ['Driver', 'Entrant', 'Constructor', 'Time/Retired', 'Grid']
Types: ['text', 'text', 'text', 'text', 'real']
Sample row: ['Peter Gethin', 'Yardley-BRM', 'BRM', '19:54.4', 2.0]
SQL:

assistant: SELECT "Constructor" FROM "Table" WHERE "Grid" < 21.0 AND "Time/Retired" = 'Engine';