user: Question: What is the average number of laps with an Accident time/retired, Aprilia manufacturer and a grid of 27?
Columns: ['Rider', 'Manufacturer', 'Laps', 'Time/Retired', 'Grid']
Types: ['text', 'text', 'real', 'text', 'real']
Sample row: ['Arnaud Vincent', 'Aprilia', 18.0, '+46:22.971', 2.0]
SQL:

assistant: SELECT AVG("Laps") FROM "Table" WHERE "Time/Retired" = 'Accident' AND "Manufacturer" = 'Aprilia' AND "Grid" = 27.0;