Realize income is a .the amount of income on hand b. income already spent c. income that comes from future investment d. the amount of income you anticipate having

The distribution of the amount of money spent by students for textbooks in a semester is approximately normal in shape with a mean of $235 and a standard deviation of $20. according to the standard deviation rule, how much did almost all (99.7%) of the students spend on textbooks in a semester?