A trash company is designing an open-top, rectangular container that will have a volume of 1715 ft cubed. The cost of making the bottom of the container is $5 per square foot, and the cost of the sides is $4 per square foot. Find the dimensions of the container that will minimize total cost.

14 ft × 14 ft × 8.75 ft

Step-by-step explanation:

A garbage company is designing an open rectangular container that should have a volume of 1,715 cubic feet.

So we have the length of the container = "x" ft, the width of the container = "y" ft and the height of the container = "z" ft

Therefore the volume of the rectangular container would be:

x * y * z = 1715 ft³

z = 1715 / x * y

The cost of making the bottom of the container is $ 5 per square foot, that is:

5 * (x * y)

Now, area of all sides of the container would be:

2 * (x * z + y * z) = 2 * z * (x + y)

We know that it has been given that the cost of making all the sides of the container is = $ 4 per square foot, so:

4 * (2 * z * (x + y)) = 8 * z * (x + y)

In total the costs would be:

5 * (x * y) + 8 * z * (x + y)

If we replace z, in the previous equation we have:

5 * (x * y) + 8 * (1715 / x * y) * (x + y)

solving, and we would have that the total cost would be:

C = 5 * (x * y) + 13720 / x + 13720 / y

Now we will find the derivative of C and make it equal to zero:

dC / dx = 0; dC / dy = 0

For dC / dx = 0:

dC / dx = 5 * y + 13720 * -1 / (y ^ 2) + 13720 * 0

0 = 5 * y - 13720 / y ^ 2

5 * y = 13720 / y ^ 2

y ^ 3 = 13720/5 = 2744

y = 14

For dC / dy = 0:

dC / dy = 5 * x + 13720 * 0 + 13720 * -1 / (x ^ 2)

0 = 5 * x - 13720 / x ^ 2

5 * x = 13720 / x ^ 2

x ^ 3 = 13720/5 = 2744

x = 14

now for z:

z = 1715 / (14 * 14)

z = 8.75

Therefore, the dimensions of the container should be 14 ft × 14 ft × 8.75 ft to minimize manufacturing cost.

is there answer choices?

correct answer:

b.(19,-2)