user: Question: How many tracks have a single density?
Columns: ['Size', 'Density', 'Tracks', 'Coercivity', 'Unformatted capacity per side']
Types: ['text', 'text', 'real', 'text', 'text']
Sample row: ['3½in', 'single', 40.0, '600Oe', '250KB']
SQL:

assistant: SELECT SUM("Tracks") FROM "Table" WHERE "Density" = 'single';