A group of veterinary researchers plan a study to estimate the average number of enteroliths in horses suffering from them Previously research has shown the variability in the number to be o 2 The researchers wish the margin of error to be no larger than 0 5 for a 99 confidence interval To obtain such a margin of error the researchers need at least OA 106 observations OB 107 observations O C 54 observations OD 53 observations