Name the highest Long that has an Avg/G smaller than 8.4, and an GP-GS of 4–0?
CREATE TABLE "rushing" (
  "name" text,
  "gp_gs" text,
  "gain" real,
  "loss" real,
  "long" real,
  "avg_g" real
);
SELECT MAX("long") FROM "rushing" WHERE "avg_g"<8.4 AND "gp_gs"='4–0';