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 $S$ .

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