6) The diameter of small Nerf balls manufactured at a factory in China is expected to be approximately normally distributed with a mean of 5.2 inches...

6)   The diameter of small Nerf balls manufactured at a factory in China is expected to be approximately normally distributed with a mean of 5.2 inches and a standard deviation of 0.8 inches. Suppose a random sample of 20 balls are selected. What percentage of sample means will be less than 5.15 inches?