CREATE TABLE table_72087 ("No. in set" FLOAT, "No. in series" FLOAT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "Original air date" TEXT, "Production code" TEXT)

What is the episode number that has production code 8abx15?
SELECT MIN("No. in series") FROM table_72087 WHERE "Production code" = '8ABX15'
SELECT MIN("No. in series") FROM "table_72087" WHERE "Production code" = '8ABX15'