What is the average upper index MJ/Nm 3 for the upper index Kcal/Nm 3 entry of 19,376?
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("upper_index_mj_nm_3") FROM "wobbe_index_of_common_fuel_gases" WHERE "upper_index_kcal_nm_3"='19,376';