What is the value of x that makes this figure correct? ​

Based on what i know about mean, this doesn't add up.

The head librarian at the library of congress has asked her assistant for an interval estimate of the mean number of books checked out each day. the assistant provides the following interval estimate: from 740 to 920 books per day. what is an efficient, unbiased point estimate of the number of books checked out each day at the library of congress?

What is the equation of the graph below? y=sec(x)-4