Cacti have been used for medicinal purposes for centuries. in the last 50 years, cacti have also because popular landscape plants. consequently, mature cacti have been dug up in the desert for sale in plant nurseries. researchers interested in the age of a certain medicinal cacti found in the arizona desert. 50 years ago, the average age of this cacti was 171 years. the researchers want to know if the average age of all cacti (of this type) living in an arizonan national forest has decreased. they take a random sample of 64 cacti found in this arizona national forest. below are the charts and plots of their data. set the population standard deviaion = 49. a. are the conditions met to calculate a 95% ci for the mean? b. find a 95% ci for the mean. c. which is the interpretation of the interval you calculated in part (b)? d. is there statistical evidence the average age of cacti has decreased?