Determine the Constant of Variation for the Stated Condition $t$ Varies Jointly As

Multiple Choice

Determine the constant of variation for the stated condition.
- $t$ varies jointly as $r$ and $s$ , and $t = 36$ when $r = 45$ and $s = 20$ .

A) $\mathrm { k } = \frac { 1 } { 25 }$
B) $\mathrm { k } = \frac { 1 } { 20 }$
C) $k = 25$
D) $\mathrm { k } = 20$