What is the highes win % that manager juan carlos chávez's team had when they lost less than 4 times?
CREATE TABLE "mexico_under_20_managers" (
  "manager" text,
  "mexico_career" text,
  "played" real,
  "drawn" real,
  "lost" real,
  "win_pct" real
);
SELECT MAX("win_pct") FROM "mexico_under_20_managers" WHERE "manager"='juan carlos chávez' AND "lost"<4;