How much Withdrawn has a Number of 42, and a Previous Number(s) larger than 68178?
CREATE TABLE "great_eastern_section" (
  "number" text,
  "previous_number_s" real,
  "previous_class" text,
  "converted" real,
  "withdrawn" real,
  "disposal" text
);
SELECT SUM("withdrawn") FROM "great_eastern_section" WHERE "number"='42' AND "previous_number_s">68178;