Can someone help solve these in the simplest way step by step. If excel is needed to get to the answer faster that is fine as well. Thank you in advance.

1.What is the lower bound of the 95% confidence interval for the following stock returns?

Year 1 - 19.1%, Year 2 - 4.7%, Year 3 - -2.5%, Year 4 - -5.7%, Year 5 - 11%, Year 6 - 9.2%

2. Coca Cola stock prices gave a realized return of 5%, -5%, 11%, and -11% over four successive quarters. What is the annual realized return for the year in Coca cola?