user: Question: What is the average capacity for the vehicle having a navigator of Macneall?
Columns: ['Driver', 'Navigator', 'Vehicle', 'Class', 'Capacity', 'Total Time', 'Margin']
Types: ['text', 'text', 'text', 'text', 'real', 'text', 'text']
Sample row: ['Glenney', 'Webb', '2003 Mitsubishi Lancer Evo 9', 'CM22', 3396.0, '07:35', '00:00']
SQL:

assistant: SELECT AVG("Capacity") FROM "Table" WHERE "Navigator" = 'Macneall';