Use the confidence interval method: For a sample of 25 items from a normally distributed population for which the standard deviation is o=10, the sample mean is 235. At the 0.05 level of significance, test Ho: u is less than or equal to 220 versus u > 220. Determine the 95% confidence interval. Is 220 a plausible value?

the second part:

Now use the p-value method to determine is 220 is plausible value. State the p-value and your conclusions. Use an alpha= 0.05.

Now, I from what I calculated, I came up with (231.08-238.92) as the 95% confidence level, which makes 220 not a plausible value. However, I am completely lost as where to go with the p-value. I have been working on this problem for hours and have gotten nowhere. Please help!