Find a Mathematical Model Representing the Statement $z = \frac { 3 x ^ { 2 } } { 4 y }$

Multiple Choice

Find a mathematical model representing the statement.(Determine the constant of proportionality. ) ​
Z varies directly as the square of x and inversely as y.(z = 36 when x = 9 and y = 3. )
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A) $z = \frac { 3 x ^ { 2 } } { 4 y }$
B) $$z = \frac { 4 x } { 3 y }$$
C) $$z = \frac { 4 x ^ { 2 } } { 3 y }$$
D) $z = - \frac { 3 x ^ { 2 } } { 4 y }$
E) $z = - \frac { 4 x ^ { 2 } } { 3 y }$