Hi, so I keeping getting the answer wrong for the last step of the problem regarding the standard deviation. I keep getting around 0.0149 for the standard deviation but I know the correct answer is 0.0258 0r 0.03. Can someone walk me through the steps so I know what I’m doing wrong?

A pipet delivers 9.04, 9.02, 9.08, and 9.06 mL in consecutive trials. Find the mean volume and the average deviation from the mean. Calculate the standard deviation for the volumes delivered by this
pipet.
mean: 9.05
average deviation; 0.02 ml