Before a book is sent for printing, Anna, a proofreader, needs to ensure that there are no grammatical or typographical errors in any page. Based on her past experiences, she found the probability for the number of errors per page in a book shown as follows:

Number of Errors Probability 2 0.19 3 0.31 Number of Errors Probability 4 0.23 5 0.14 6 0.13

a. What is the probability that a book has 4 or more errors in a page?

b. Compute the average number of errors per page in a book.

c. Calculate the standard deviation for errors per page in a book and interpret it.