Apples cost $2.20 per kilogram. samuel need 500 grams of apples to put in a fruit salad. how much will he need to buy

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?