Calculate the derivatives using implicit differentiation, where c is a constant:
$\frac{\partial U}{\partial T}$ and $\frac{\partial T}{\partial U}$ of $(TU-V)^2 \ln(W-UV) = c$ at $(T, U, V, W) = (7, 1, 9, 18)$
$\frac{\partial U}{\partial T}|_{(7,1,9,18)} = \boxed{}$
$\frac{\partial T}{\partial U}|_{(7,1,9,18)} = \boxed{}$