Write an Equation to Describe the Variation $P$ Varies Jointly As $R$

Multiple Choice

Write an equation to describe the variation. Use k for the constant of proportionality.
- $P$ varies jointly as $R$ and the square of $S$ .

A) $P + R + S ^ { 2 } = k$
B) $\mathrm { PRS } ^ { 2 } = \mathrm { k }$
C) $P = k R S ^ { 2 }$
D) $P = k + R + S ^ { 2 }$