Cost of Material. A rectangular box with volume 320 ft3 is built with a square base and to...

Cost of Material. A rectangular box with volume 320 ft3 is built with a square base and top. The cost is $1.50/ft2 for the bottom, $2.50/ft2 for the sides, and $1/ft2 for the top. Let x = the length of the base, in feet.

a) Express the cost of the box as a function of x.

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b) Find the domain of the function.

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c) Graph the function with a graphing calculator.

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d) What dimensions minimize the cost of the box?