what is the total number of player where years for rockets is 1975-79
CREATE TABLE "w" (
  "player" text,
  "no_s" text,
  "height_in_ft" text,
  "position" text,
  "years_for_rockets" text,
  "school_club_team_country" text
);
SELECT COUNT("player") FROM "w" WHERE "years_for_rockets"='1975-79';