How can I solve this question?

Please give me a full explanation.

Consider the hyperbolic paraboloid z = x2 y2 . A drone is programmed to y along the surface of the hyperbolic paraboloid. The ight instruments measure the velocity in the x, y and z directions as dx _ d)' _ _ dt _ 4 dt _ 1 dt _ 1 ' The GPS measures A: = 40 , but the GPS does not measure y (to keep costs down). What is the y co-ordinate? The chain rule can tell us! It's