Question 3 Suppose that z varies jointly with the cube of x and the square of y. Find the constant of proportionality k if z = 80 when y = 2 and x = 2. 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 = 9 and x = 7. Z = If needed, round answer to 3 decimal places. Enter DNE for Does Not Exist, oo for Infinity