Write an Equation to Describe the Variation $t$
A) $\mathrm { rs } ^ { 2 } \mathrm { t } ^ { 3 } = \mathrm { k }$

Multiple Choice

Write an equation to describe the variation. Use k for the constant of proportionality.
-r varies directly as the square of s and inversely as the cube of $t$ .

A) $\mathrm { rs } ^ { 2 } \mathrm { t } ^ { 3 } = \mathrm { k }$
B) $r = \frac { k s ^ { 2 } } { t ^ { 3 } }$
C) $r + s ^ { 2 } - t ^ { 3 } = k$
D) $r = \frac { k t ^ { 3 } } { s ^ { 2 } }$