Find the first partial derivatives of $f(x,y,z) = z \ \arctan(\frac{y}{x})$ at the point (2, 2, 1).

A. $\frac{\partial f}{\partial x}(2, 2, 1) =$

B. $\frac{\partial f}{\partial y}(2, 2, 1) =$

C. $\frac{\partial f}{\partial z}(2, 2, 1) =$