The owner of a senior living facility examines data on the age of the residents at the facility. She finds that the distribution of ages of residents is approximately normal with a mean of 73.5 years and a standard deviation of 6.5 years. Which interval below estimates the middle 99.7% of ages of residents living at the facility?
a. (52,95)
b. (54,93)
c. (60.5, 86,5)
d. (67,80)