What is the highest S ÷ D with a 2420 (220) [3H] paroxetine and an N ÷ D less than 393.8?
CREATE TABLE "pharmacotherapy_for_cocaine_abuse" (
  "3_h_cft" real,
  "3_h_nisoxetine" text,
  "3_h_paroxetine" text,
  "n_d" real,
  "s_d" real
);
SELECT MAX("s_d") FROM "pharmacotherapy_for_cocaine_abuse" WHERE "3_h_paroxetine"='2420 (220)' AND "n_d"<393.8;