What is the total amount of grid when the laps amount was smaller than 68 and the time/retired was injection?
CREATE TABLE "classification" (
  "driver" text,
  "constructor" text,
  "laps" real,
  "time_retired" text,
  "grid" real
);
SELECT SUM("grid") FROM "classification" WHERE "laps"<68 AND "time_retired"='injection';