Chapter 1: School on Saturday!!! And a Difficult Choice...

Mr. Morris, the principal was very mad that the students had painted their classroom with purple swirls and gray polka-dots. Not only did Mr. Morris hate polka dots, but purple was his least favorite color.
"I am very disappointed in you," said Mr. Morris, "I am sure that your parents will be very upset when they hear about this."
"Our parents?" Do you have to tell our parents?" cried Serena. Serena was one of the best students in the school and her parents were going to be very upset if they found out that she and some of her friends had decided to paint the classroom purple.
"Not only am I going to tell your parents," said Mr. Morris, "but as a punishment you are going to have to come to school for 8 hours of extra school work for the next 5 Saturdays with your teacher, Mr. R.!"

How many hours were the students going to have to come to school for in total over the next 5 Saturdays?