What is the location that has a date of demolition of 1940 and has a church named Christ Church Greyfriars?
CREATE TABLE "tower_remains" (
  "church_name" text,
  "location" text,
  "rebuilt" text,
  "date_of_demolition" real,
  "subsuming_parish" text
);
SELECT "location" FROM "tower_remains" WHERE "date_of_demolition"=1940 AND "church_name"='christ church greyfriars';