Table schema:
CREATE TABLE table_name_59 (upper_index_kcal__nm_3 VARCHAR, fuel_gas VARCHAR, lower_index_mj__nm_3 VARCHAR)

Question: What is the Upper index Kcal/ Nm 3 of iso-butane, and a Lower index MJ/ Nm 3 smaller than 84.71?
SQL: SELECT COUNT(upper_index_kcal__nm_3) FROM table_name_59 WHERE fuel_gas = "iso-butane" AND lower_index_mj__nm_3 < 84.71