In each case, determine if the distribution of the sample mean (x-bar) is NORMALLY DISTRIBUTED, AT LEAST APPROXIMATELY NORMALLY DISTRIBUTED, or CANNOT BE DETERMINED. a: The population is known to be normally distributed, the sample size is n = 56. b: The population distribution is not known, sample size is n = 100. c: The population is known to be normally distributed, sample size is n = 15. d: The population distribution is unknown, sample size is 15.