I think it's C) but the answer should be 6561.
3 groups and 8 people...

Will give you your answer
Answer:
13655.90016
Step-by-step explanation:

Hi there!
![\large\boxed{f^{-1}(x) = \sqrt[3]{\frac{x+4}{9} } }](https://tex.z-dn.net/?f=%5Clarge%5Cboxed%7Bf%5E%7B-1%7D%28x%29%20%3D%20%20%5Csqrt%5B3%5D%7B%5Cfrac%7Bx%2B4%7D%7B9%7D%20%7D%20%7D)

Find the inverse by replacing f(x) with y and swapping the x and y variables:

Isolate y by adding 4 to both sides:

Divide both sides by 9:

Take the cube root of both sides:
![y = \sqrt[3]{\frac{x+4}{9} }\\\\f^{-1}(x) = \sqrt[3]{\frac{x+4}{9} }](https://tex.z-dn.net/?f=y%20%3D%20%5Csqrt%5B3%5D%7B%5Cfrac%7Bx%2B4%7D%7B9%7D%20%7D%5C%5C%5C%5Cf%5E%7B-1%7D%28x%29%20%3D%20%5Csqrt%5B3%5D%7B%5Cfrac%7Bx%2B4%7D%7B9%7D%20%7D)