The answer for this problem is b
That easy just divide 9 by 22 if need simplify it
Answer: 
Step-by-step explanation:
Given
The unit cost is given by

find the derivative of the unit cost and equate it to zero to obtain the minimum value

Substitute 140 for
in the cost function, we get
![C(140)=0.6[140]^2-168(140)+30,389\\C(140)=11,760-23,520+30,389\\C(140)=\$18,629](https://tex.z-dn.net/?f=C%28140%29%3D0.6%5B140%5D%5E2-168%28140%29%2B30%2C389%5C%5CC%28140%29%3D11%2C760-23%2C520%2B30%2C389%5C%5CC%28140%29%3D%5C%2418%2C629)
Area = length x width
f(x) = (x + 5)(3x - 7)
f(x) = 3x^2 + 8x - 35