user: Question: Name the number of stations for 15 minutes travel time
Columns: ['Lines', 'Opening', 'Traction', 'Length', 'Stations', 'Route', 'Stops', 'Travel time']
Types: ['text', 'real', 'text', 'text', 'real', 'text', 'real', 'text']
Sample row: ['Naples – Baiano', 1885.0, 'Electric', '38 km', 28.0, 'Porta Nolana - Nola - Baiano', 28.0, '59 minutes']
SQL:

assistant: SELECT "Stations" FROM "Table" WHERE "Travel time" = '15 minutes';