The table below shows the rate of books being checked out (in books per hour) from the local library at various times (in hours) during the day.

1. About how many books were checked out during the day?

   Hint (a):

   This is the area under $b^\prime$.

2. What was the average rate of books being checked out?

   Hint (b):

   $\text{This is }\frac{\text{total books checked out}}{\text{total hours}}.$

   You computed the total books check out in part (a).
   What is the total number of hours?