During the holidays, Duncan works as a gift wrapper. He works 35 hours a week, spread equally over 5 workdays. If Duncan earns $9 an hour, how much does he make on each workday?

Last month, a 770 g box of cereal was sold at a grocery store for $3.10. however, this month, the cereal manufacturer launched the same cereal in a 640 g box, which is being sold at $2.50. what is the percent change in the unit price?