If x2 + y2 + z2 = 9, dx / dt = 5, and dy /d1 = 4, find dz/ dt when (x, y, z) = (2, 2, 1)

If x2 + y2 + z2 = 9, dx / dt = 5, and dy /d1 = 4,
find dz/ dt when (x, y, z) = (2, 2, 1).