Need both much appreciated

Check my The highway fuel economy of a 2016 Lexus RX 350 FWD 6-cylinder 3.5-L automatic 5-speed using premium fuel is a normally distributed random variable with a mean of # = 21.50 mpg and a standard deviation of o = 2.75 mpg. (a) What is the standard error of X" , the mean from a random sample of 9 fill-ups by one driver? (Round your answer to 4 decimal places.) Standard error of X 0.5625 (b) Within what interval would you expect the sample mean to fall, with 95 percent probability? (Round your answers to 4 decimal places.) The interval is from