CREATE TABLE table_77986 ("Line" CLOB, "Began operation" FLOAT, "Stations" FLOAT, "Length  ( km ) " CLOB, "Terminals" CLOB)

What is the average operation beginning with a length of ampang and over 27 stations?
SELECT AVG("Began operation") FROM table_77986 WHERE "Length (km)" = 'ampang' AND "Stations" > '27'
SELECT AVG("Began operation") FROM "table_77986" WHERE "Length (km)" = 'ampang' AND "Stations" > '27'