A Formula Is Given, Along with Values for All but One

Multiple Choice

A formula is given, along with values for all but one of the variables in the formula. Find the value of the variable that is not given.
- $C=2 \pi r ; r=9, \pi=3.14$

A) $\mathrm{C}=354.95$
B) $\mathrm{C}=59.66$
C) $\mathrm{C}=18$
D) $\mathrm{C}=56.52$