user: Question: What is the average grid for Piers Courage?
Columns: ['Driver', 'Constructor', 'Laps', 'Time/Retired', 'Grid']
Types: ['text', 'text', 'real', 'text', 'real']
Sample row: ['Denny Hulme', 'McLaren - Ford', 65.0, '1:54:08.80', 4.0]
SQL:

assistant: SELECT AVG("Grid") FROM "Table" WHERE "Driver" = 'Piers Courage';