Question 1196390
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            Problem does not say that the area remains the same.

            THEREFORE,  by default,  I will assume/interpret that the length is not changed.



Part  (a)  is very simple.


When the width increased from 200 ft to 400 ft, three dimensions increased from 200 to 400 ft  (see the referred plot).


Therefore, &nbsp;the total increase of the whole fence, &nbsp;including the internal partition is &nbsp;&nbsp;3*200 = 600 ft.&nbsp;&nbsp;&nbsp;&nbsp;<U>ANSWER</U>



Part/question &nbsp;(b) &nbsp;makes no sense and can not be answered,

because the concept &nbsp;" rate " &nbsp;assumes that time interval is given in the problem, &nbsp;which is not the case.