What is the amount of Avg/G with a Name of blaine gabbert and a Long greater than 30?
CREATE TABLE "rushing" (
  "name" text,
  "gp_gs" real,
  "gain" real,
  "loss" real,
  "long" real,
  "avg_g" real
);
SELECT SUM("avg_g") FROM "rushing" WHERE "name"='blaine gabbert' AND "long">30;