<span>The sub-boxes will have dimensions
x sub-intervals are 0 to 1 and 1 to 2. Midpoints are at

and </span><span>
y sub-intervals are 0 to 1 and 1 to 2. Midpoints are at </span><span>

and </span><span>
z sub-intervals are 0 to 1 and 1 to 2. Midpoints are at </span><span>

and </span><span><span>

</span>
Let


</span>
Y2-y1/x2-x1
(1,14) & (3,4)
y2= 4
y1=14
x2=3
x1=1
So....
(4-14)/(3-1) = -10/2 = -5
The answer should be negative instead of positive, she probably subtracted 4 from 14 instead.