Assume that the duration of human pregnancies can be described by a Normal model with mean 268 days and standard deviation 1? days. a) What percentage of pregnancies should last between 272 and 281 days? k. b) At least how many days should the longest 20% of all pregnancies last? c) Suppose a certain obstetrician is currently providing prenatal care to 52 pregnant women. Let 9 represent the mean length of their pregnancies. According to the Central Limit Theorem, what's the distribution of this sample mean, )7? Specify the model. mean. and standard deviation. d) What's the probability that the mean duration of these patients' pregnancies will be less than 259 days? a) The percentage of pregnancies that should last between 272 and 281 days is [:I%. (Round to two decimal places as needed.) b) The longest 20% of all pregnancies should last at least [3 days. (Round to one decimal place as needed.) c) Select the correct choice below and, if necessary. ll in the answer box(es) within your choice. GA. A Normal model with mean D and standard deviation 1:] (Type integers or decimals rounded to two decimal places as needed.) A Binomial model with D trials and a probability of success of D (Type integers or decimais rounded to two decimal places as needed.) 0 C. There is no model that ts this distribution. OB. d) The probability that the mean duration of these patients' pregnancies will be less than 259 days is D (Round to four decimal places as needed.)