The amount spent on textbooks for the fall term was recorded for a sample of five hundred university students.

The amount spent on textbooks for the fall term was recorded for a sample of five hundred university students. The mean explenditure was calculated to be $500 and the standard deviation of the expenditures was calculated to be $100. Suppose a randomly selected student reported that their text book expenditure was $700. Calculate the z-score for this student's textbook expenditure.