Suppose that z varies jointly with x and y.

Find the constant of proportionality k if z = 121.5 when y = 9 and x = 5.
k =
Using the k from above write the variation equation in terms of x and y.
z =
Using the k from above find z given that y = 20 and x = 10.
z =

If needed, round answer to 3 decimal places.
Enter DNE for Does Not Exist, oo for Infinity