ANSWER
The midline y=3.6
EXPLANATION
The midline is the midpoint of the peak value and the least value.
The peak value is 5.20
The least value is 2
The midline is
[tex]y = \frac{5.20 + 2}{2} = \frac{7.2}{2} = 3.6[/tex]
Therefore the mid value is y=3.6
