A study investigating the relationship between age and annual medical expenses randomly samples 400 individuals in a city. It is hoped that the sample will have a similar mean age as the entire population. Complete parts a and b below. a. If the standard deviation of the ages of all individuals in the city is o = 12, find the probability that the mean age of the individuals sampled is within one year of the mean age for all individuals in the city. (Hint: Find the sampling distribution of the sample mean age and use the central limit theorem. You don't have to know the population mean to answer this, but if it makes it easier, use a value such as u = 30.) The probability is. (Round to three decimal places as needed.) b. Would the probability be larger, or smaller, if o = 5? Why? If o were smaller, the standard deviation of the sampling distribution would be so the probability would be