If $$ y $$ varies jointly with $$ x $$ and $$ z $$ , and $$ ...

Question Analysis
This problem assesses the ability to find the constant of variation in a joint variation problem.

Key Concept Explanation
In joint variation, the formula is . To find the constant of variation , substitute the given values into the formula and solve for .

Step-by-step Solution
1. Substitute the given values into the formula:
2. Simplify the equation: