(09.07 LC) In a study of 250 adults, the mean heart rate was 70 beats per minute. Assume the population of heart rates is known to be approximately normal with a standard deviation of 12 beats per minute. What is the 99% confidence interval for the mean beats per minute? (6 points)
A. 68.9-76.3
B. 70-72
C. 61.2-72.8
D. 68-72