Solve the Problem $C$ Is a Simple Closed Path, What Is Special About the What

Short Answer

Solve the problem.
-Assuming $C$ is a simple closed path, what is special about the integral
$\left. \left. \int _ { C } \left( 6 x + 8 e ^ { 9 x } \cos 9 y \right) \right) d x + \left( 3 x + 8 e ^ { 9 x } \sin 9 y \right) \right) d y ?$ Give reasons for your answer.