If the rectangle has a fixed width of 300, it means that
where 
and 
are width and length, respetively.
So given the length , the are would be
You want to find the monthly average over the past 6 months.
July: $78.56
August: $30.21
September: $81.20
October: $79.08
November: $66.18
December: $100.75
Add all of these up
(July) $78.56
(August) $30.21
(September) $81.20
(October) $79.08
(November) $66.18
(December) + $100.75
----------------------------------------------
(Total cost) $435.88
There are 6 months you are calculating for, therefore divide the total (combined) cost of 6 months with the total number of months (in this case, 6)
$435.88 (total cost of 6 months) ÷ 6 (months)
The average cost per month of over the past 6 months is $72.66.
Check the one-sided limits:
If <em>f(x)</em> is to be continuous at <em>x</em> = 5, then these two limits should have the same value, which means
5<em>k</em> = 200
<em>k</em> = 200/5
<em>k</em> = 40
The answer is 15 to the question
