Which interval has the greatest slope or the steepest portion!!
(1) hour 0 to hour 1, the y value changed from 0 to 2
(2) hour 1 to hour 2, the y value changed from 2 to 3.5
(3) hour 2 to hour 3, the y value changed from 3.5 to 4.5
(4) hour 3 to hour 4, the y value changed from 4.5 to 5
So which has the greatest rate of change?  We can also look at the graph and see the portion that is the steepest.

That’s it!! 2 points