Lisa reads an equal number of pages of a book every week. The graph below shows the number of pages of the book left to read, y, after x weeks: A graph titled Lisas Book Reading shows Number of Weeks on the x-axis and Number of Pages Left on the y-axis. The scale on the x-axis shows numbers from 0 to 6 at increments of 1, and the scale on the y-axis shows numbers from 0 to 350 at increments of 50. A straight line joins the ordered pairs 0, 250 and 1, 200 and 2, 150 and 3, 100 and 4, 50 and 5, 0.

Which equation best models the relationship between x and y?

y = −50x + 250
y = −5x + 50
y = −50x + 350
y = −5x + 250