CREATE TABLE table_19168 ("State" CLOB, "Highest point" CLOB, "Highest elevation" CLOB, "Lowest point" CLOB, "Lowest elevation" CLOB, "Mean elevation" CLOB)

what's the lowest point with highest point being mount greylock
SELECT "Lowest point" FROM table_19168 WHERE "Highest point" = 'Mount Greylock'
SELECT "Lowest point" FROM "table_19168" WHERE "Highest point" = 'Mount Greylock'