Let U be the solid enclosed by y = x^2+ z^2 and y =9. In this problem, youll find the average value of the functions f (x, y, z)= sin z and g(x, y, z)=\sqrt(y) on U. (a) You can find the average value of one of f and g on U without doing any computation. Which one? Whats its average value, and why? (b) Before finding the average value of the other function, make a rough estimate of the average value, and explain how you got your estimate. Then calculate the average value exactly.