What's the mean of the $70-80k ones that have 2.80%?
CREATE TABLE "faculty_and_staff" (
  "data" text,
  "headcount" real,
  "percent_of_total" text,
  "less_than_25_000" text,
  "25_000_to_40_000" text,
  "40_000_to_50_000" text,
  "50_000_to_60_000" text,
  "60_000_to_70_000" text,
  "70_000_to_80_000" text,
  "more_than_80_000" text,
  "mean" text
);
SELECT "mean" FROM "faculty_and_staff" WHERE "70_000_to_80_000"='2.80%';