What is the average share at 8:00 p.m., and an 18-49 of 1.3/4 with an air date of April 4, 2008?
CREATE TABLE "u_s_standard_ratings" (
  "air_date" text,
  "timeslot" text,
  "rating" real,
  "share" real,
  "18_49" text,
  "viewers" real,
  "weekly_rank" text
);
SELECT AVG("share") FROM "u_s_standard_ratings" WHERE "timeslot"='8:00 p.m.' AND "18_49"='1.3/4' AND "air_date"='april 4, 2008';