user: Question: What is the max speed of the unit with an 8+4 quantity built before 1971?
Columns: ['Type', 'Numbers', 'Year built', 'Quantity built', 'Power (horsepower)', 'Max Speed (km/h)']
Types: ['text', 'text', 'real', 'text', 'real', 'real']
Sample row: ['RHN', '1011-1048 (power cars) 11-48 (trailer cars)', 1967.0, '38+38', 220.0, 90.0]
SQL:

assistant: SELECT "Max Speed (km/h)" FROM "Table" WHERE "Quantity built" = '8+4' AND "Year built" < 1971.0;