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

### Instruction:
What is the Upper index Kcal/ Nm 3 of iso-butane, and a Lower index MJ/ Nm 3 smaller than 84.71?

### Inputs:
table_name: table, columns: ['Fuel gas', 'Upper index Kcal/ Nm 3', 'Lower index Kcal/ Nm 3', 'Upper index MJ/ Nm 3', 'Lower index MJ/ Nm 3']

### Response:
SELECT COUNT Upper index Kcal/ Nm 3 FROM table WHERE Fuel gas = iso-butane AND Lower index MJ/ Nm 3 < 84.71