One who purchases [grain] for seed or for [feeding] animals, flour for [tanning] hides, oil for a lamp or oil for greasing utensils is exempt from the demai [tithing obligation]. From Keziv and beyond is exempt from the demai [tithing obligation]. The challah of an am haaretz, produce mixed with terumah, that which is pur-chased with maaser sheni money and the remnants of minchah-offerings are exempt from the demai [tithing obligation]. Pleasant oil: Beis Shammai [consider it] liable [to the demai tithing obligation]; but Beis Hillel exempt [it].