Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_64437 ( "Fuel gas" text, "Upper index Kcal/ Nm 3" real, "Lower index Kcal/ Nm 3" real, "Upper index MJ/ Nm 3" real, "Lower index MJ/ Nm 3" real )

### Question ###
What is the entry for Lower index MJ/ Nm 3 for the row that has an Upper index Kcal/ Nm 3 larger than 19,376, for lpg, and an Upper index MJ/ Nm 3 smaller than 86.84?

### Accurate SQL ###

SELECT AVG("Lower index MJ/ Nm 3") FROM table_64437 WHERE "Upper index Kcal/ Nm 3" > '19,376' AND "Fuel gas" = 'lpg' AND "Upper index MJ/ Nm 3" < '86.84'