The initial value of the graph is where 
. Thus, in this case, the initial value is 12.
The rate of change of the graph is essentially the slope of the graph. In this case, we can use the slope formula:
and 
are points on the graph
Let's use two points from the chart to find the slope:
In this case, the rate of change of the graph is 9.
In one minute printer can make 12/3=4 photos
1st box so in 4 minutes it will make 4*4 = 16 photos
2nd box 24 images will be in 24/4= 6 minutes
3rd box in 9 minutes it will make 9*4=36 images
4th box 40 images will be 40/4=10 minutes
The answer to your question is 1
