Problem 9. Prove each statement using proof by contradiction. 9(a) If a person buys at least 400 cups of coffee in a year, then there is at least one day in which the person has bought at least two cups of coffee. 9(b) If a group of 9 kids have won a total of 100 trophies, then at least one of the 9 kids has won at least 12 trophies