I need help plzz time test

The first-serve percentage of a tennis player in a match is normally distributed with a standard deviation of 4.3%. if a sample of 15 random matches of the player is taken, the mean first-serve percentage is found to be 26.4%. what is the margin of error of the sample mean? a. 0.086% b. 0.533% c. 1.11% d. 2.22%

Which one is the correct answer, and why?

In triangle △abc, ∠abc=90°, bh is an altitude. find the missing lengths. ac=26 and ch=8, find bh.