The scores on a psychology exam were normally distributed with a mean of 71 and a standard deviation of 5 . A failing grade on the exam was anything 2 or more standard deviations below the mean. What was the cutoff for a failing score? Approximately what percentage of the students failed?

I understand the first part of the question. I need help understanding the second part, would you be able to go step by step so that I can understand? Thank you