The leading brand of cosmetics in the US had about 20% of the total sales in the industry. The total sales were $2.6 billion. What was the leading brands sales?

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?