sarah gets paid $100. she also gets a commission of $200 per lawn mower she sells. if her pay can be modeled as y = 200x + 100, how much money does she make if she sells 4 lawnmowers

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?