An ecological group suspects dolphins are consuming dangerous levels of arsenic in a region of the world. Dangerous levels of arsenic are classified when they reach beyond 7.0 parts per million. A random sample of 28 dolphins in the region were tested and the data is shown in the stemplot.
Arsenic Levels
2 4
2
3 23
3 679
4 013
4 577
5 01144
5 78
6 34
6 6
7 013
7 567
Key: 214 2.4 parts per million
Part A: What proportion of the dolphins in the sample have dangerous levels of arsenic in their systems? (4 points)
Part B: Construct and interpret a 99% confidence interval for the mean arsenic levels of the dolphins if the sample of 28 dolphins has a mean arsenic level of 5.26
parts per million and standard deviation of 1.49 parts per million (6 points

30 POINTS PLEASE HELP!!!