8. Show that f(x,y) =
is continuous at every point except the origin. (10%)
7. Water runs into a conical tank at the rate of 9 ft³/min. The tank stands point down and has a height of 10 ft and a base radius of 5 ft. How fast is the water level rising when the water is 6 ft deep? (see the figure below) (10%)
the conical tank in problem 7.