Answer:
(a)Length =2 feet
(b)Width =2 feet
(c)Height=3 feet
Step-by-step explanation:
Let the dimensions of the box be x, y and z
The rectangular box has a square base.
Therefore, Volume of the box
Volume of the box

The material for the base costs
, the material for the sides costs
, and the material for the top costs
.
Area of the base 
Cost of the Base 
Area of the sides 
Cost of the sides=
Area of the Top 
Cost of the Base 
Total Cost, 
Substituting 

To minimize C(x), we solve for the derivative and obtain its critical point
![C'(x)=\dfrac{0.6x^3-4.8}{x^2}\\Setting \:C'(x)=0\\0.6x^3-4.8=0\\0.6x^3=4.8\\x^3=4.8\div 0.6\\x^3=8\\x=\sqrt[3]{8}=2](https://tex.z-dn.net/?f=C%27%28x%29%3D%5Cdfrac%7B0.6x%5E3-4.8%7D%7Bx%5E2%7D%5C%5CSetting%20%5C%3AC%27%28x%29%3D0%5C%5C0.6x%5E3-4.8%3D0%5C%5C0.6x%5E3%3D4.8%5C%5Cx%5E3%3D4.8%5Cdiv%200.6%5C%5Cx%5E3%3D8%5C%5Cx%3D%5Csqrt%5B3%5D%7B8%7D%3D2)
Recall: 
Therefore, the dimensions that minimizes the cost of the box are:
(a)Length =2 feet
(b)Width =2 feet
(c)Height=3 feet
−
9
Explanation:
(
3
i
)
2
=
9
i
2
i
2
=
−
1
,
therefore,
9
i
2
=
9
⋅
(
−
1
)
=
−
9
Okay! 4/16= 0.25 because 16/16 = 1 and so that means 12/16 = 0.75 and 8/16 = 0.50 and 4/16 = 0.25 Hope this helped!