Yashchin (1995) discusses a process for the chemical etching of silicon wafers used in integrated circuits. This process etches the layer of silicon dioxide until the layer of metal beneath is reached. This company monitors the thickness of the silicon oxide layer because thicker layers require longer etching times. Historically, the layer of thicknesses have a standard deviation of 0.06 micron. Find the sample size required to estimate the true mean thickness to within ± 0.01 micron using a 95% confidence.