The variable z varies jointly with the third powers of x and y. If z = 2160 when x = 3 and y = 4, find z when x = 2 and y = 5.

The variable z varies jointly with the second power of x and the third power of y. Find the constant of proportionality if z = 2160 when x = 3 and y-4 and then find z when x = 2 and y=5