Find an Equation of Variation in Which the Following Are $y$

Multiple Choice

Find an equation of variation in which the following are true.
- $y$ varies jointly as $x$ and $z$ , and $y = 175$ when $x = 5$ and $z = 7$

A) $y = \frac { 175 } { x Z }$
B) $y = 5 x z$
C) $y = 35 x$
D) $y = 7 x z$