CREATE TABLE table_name_22 (max_speed__km_h_ INT, quantity_built VARCHAR, year_built VARCHAR)

What is the max speed of the unit with an 8+4 quantity built before 1971?
SELECT SUM(max_speed__km_h_) FROM table_name_22 WHERE quantity_built = "8+4" AND year_built < 1971
SELECT SUM("max_speed__km_h_") FROM "table_name_22" WHERE "8+4" = "quantity_built" AND "year_built" < 1971