4 Suppose the sediment density g cm of a randomly selected specimen from a certain region is normally distrib uted with mean 2 65 and standard deviation 85 suggested in Modeling Sediment and Water Column Interactions for Hydrophobic Pellutants Water Research 1984 a If a random sample of 25 specimens is selected what is the probability that the sample average sediment density is at most 3 00 Between 2 65 and 3 007 b How large a sample size would be required to ensure that the first probability in part a is at least 997