Fitch Proof Exercise 13.8 I am having trouble solving this Fitch Proof. Here is how far I’ve gotten ![enter image description here]( Only the last step is not checked out in Fitch but I think the logic works well. Any help is appreciated. Thank you

$$\begin{array} {rl} & \forall x .(Cx \to \forall y. (Dy \to Fxy)) \\\ & \quad \boxed{b} \\\ & \quad \quad \boxed{c} \\\ & \quad \quad \quad Cb \land Dc \\\ & \quad \quad \quad \vdots \\\ & \quad \quad \quad Fbc \\\ & \quad \quad (Cb \land Dc) \to Fbc \\\ & \quad \forall y .(Cb \land Dy) \to Fby \\\ & \forall x .\forall y. (Cx \land Dy) \to Fxy \\\ \end{array}$$

Organizing your proof like this may work. Unfortunately the software is closed so it can't be openly verified.