<PRE><B>Question 1182922</B>
The average cost is C(x)=(700+100x)/x
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C(15)=(2200/15)=$146.67
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{{{graph(300,300,-5,22,-100,2500,(700+100x)/x)}}}
the vertical asymptote is infinite cost at time 0, which makes no physical sense but is mathematically true.
the horizontal asymptote is $100 per year after enough years that the original cost is insignificant compared to the amount of electricity paid for.

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Looking at the average cost for 20 years, assuming everything else is the same except the original cost was $1000, and the average cost is (1000+2000)/20=$150.
For an average cost of $3.33 more at the end one waits 5 more years before one must buy another refrigerator.</PRE>