Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
What is the max speed of the unit with an 8+4 quantity built before 1971?

### Inputs:
table_name: table, columns: ['Type', 'Numbers', 'Year built', 'Quantity built', 'Power (horsepower)', 'Max Speed (km/h)']

### Response:
SELECT SUM Max Speed (km/h) FROM table WHERE Quantity built = 8+4 AND Year built < 1971