Let f be a function for which f(x / 3)=x^{2}+x+1. Find the sum of all values of z for which f(3 z)=7.

**Answer Choices**

A. -1 / 3

B. -1 / 9

C. 0

D. 5 / 9

E. 5 / 3

Let f be a function for which f(x / 3)=x^{2}+x+1. Find the sum of all values of z for which f(3 z)=7.

**Answer Choices**

A. -1 / 3

B. -1 / 9

C. 0

D. 5 / 9

E. 5 / 3