Needing help with this question, last tutor I got help from gave incorrect answer and explanation

A marine biologist would like to estimate the mean lifespan of all Florida manatees. The mean lifespan of a random sample of 39 Florida manatees was found to be 56.5 years. The standard deviation of the lifespans of all Florida Manatees is known to be 8 years. Using an 80% confidence level, determine a confidence interval for the mean lifespan of all Florida Manatees. Report the confidence interval using interval notation. Round solutions to two decimal places, if necessary. An 80% confidence interval is given by [54.8063,58.1397 ] x Suppose the population standard deviation was unknown, but the marine biologist found the standard deviation of the lifespan of the sample of 39 Florida manatees was 9.1 years (along with the sample mean of 56.5 years). Determine a 80% confidence interval for the mean lifespan of all Florida manatees using this new information An 80% confidence interval is given by [54.6348,58.3652 ] x protists fungi hel....pptx