Determine the Constant of Variation for the Stated Condition $r$ , And

Multiple Choice

Determine the constant of variation for the stated condition.
-s varies directly as $r$ , and $\mathrm { s } = 9$ when $\mathrm { r } = 117$ .

A) $\mathrm { k } = \frac { 1 } { 13 }$
B) $\mathrm { k } = 12$
C) $\mathrm { k } = 13$
D) $\mathrm { k } = 108$