In the spring of 1984, concern arose over the presence of ethylene dibromide, or edb, in grains and cereals. edb has the molecular formula c2h4br2 and until 1984 was commonly used as a plant fumigant. the federal limit for edb in finished cereal products is 30.0 parts per billion (ppb), where 1.0 ppb = 1.0 ✕ 10−9 g of edb for every 1.0 g of sample. how many molecules of edb are in 1.9 lb of flour if 31.5 ppb of edb is present?