Question 1113251
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The average cost per wheel is {{{(0.03x^3-4.5x^2+171x)/x = 0.03x^2-4.5x+171}}}.<br>
That is a quadratic function which is easy to analyze.  The minimum cost per wheel is when {{{x = -b/(2a) = 4.5/(2*0.03) = 75}}}.<br>
The minimum average cost is {{{0.03(75^2)-4.5(75)+171 = 2.25}}}.