Help with the following 3 questions

9. A study of 35 bolts of carpet showed that their average length was 74.2 yards. The standard deviation of the population is 1.6 yards. Which of the following is the 90% condence interval for the mean length per bolt of carpet? 10. What is the 95% condence interval for the standard deviation of birth weights at County General Hospital, if the standard deviation of the last 25 babies born there was 1.1 pounds? 11. A scientist claims that only 64% of geese in his area y south for the winter. He tags 75 random geese in the summer and nds that 24 of them do not y south in the winter. If a. = .05, is the scientist's belief warranted