SCHEMA:
CREATE TABLE table_name_21 (height__cm_ INTEGER, weight__kg_ VARCHAR, birthdate VARCHAR)
USER:
What is the height of the player born on June 24, 1964, with a weight over 84 kg?

QUERY:
SELECT AVG(height__cm_) FROM table_name_21 WHERE weight__kg_ > 84 AND birthdate = "june 24, 1964"