In the comedy Arsenic and Old Lace, two elderly sisters poisoned their gentlemen roomers with elderberry wine that contained arsenic. (The wine also contained strychnine and a pinch of cyanide, but let’s ignore those.) They got no help from their nephew, played by Cary Grant; but then, he knew nothing of median effective doses or dose-response curves. Since you do, what advice could you give the elderly sisters to make sure the wine was lethal without wasting a lot of arsenic?