Table schema:
CREATE TABLE table_name_50 (sio_2 INTEGER, na_2_o VARCHAR, k_2_o VARCHAR, fe_2_o_3 VARCHAR)

Question: What is the highest SiO 2, when K 2 O is greater than 0.16, when Fe 2 O 3 is greater than 0.16, and when Na 2 O is less than 7.53?
SQL: SELECT MAX(sio_2) FROM table_name_50 WHERE k_2_o > 0.16 AND fe_2_o_3 > 0.16 AND na_2_o < 7.53