function[f,J] = fn2(X)
    
% This is a matlab function that evaluates a function f and its derivative.
  x = X(1);
  y = X(2);
  z = X(3);

  f = [x*y - z^2 - 1; ...
       x*y*z + y^2 - x^2 - 2; ...
       exp(x) + z - exp(y) - 3];
  
  J = [y,          x,          -2*z;...
       y*z - 2*x,  x*z + 2*y,  x*y;...
       exp(x),     exp(y),     1];