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?
CREATE TABLE "wobbe_index_of_common_fuel_gases" (
  "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
);
SELECT AVG("lower_index_mj_nm_3") FROM "wobbe_index_of_common_fuel_gases" WHERE "upper_index_kcal_nm_3">'19,376' AND "fuel_gas"='lpg' AND "upper_index_mj_nm_3"<86.84;