- The perimeter of parallelogram $\(A B C D\)$ is 36 , so the sum of the lengths of adjacent sides is:

$$
\(A B+B C=18\) .
$$

- The diagonal $\(A C\)$ in a parallelogram is always less than or equal to the sum of the two adjacent sides $\(A B\)$ and $\(B C\)$.
- That means:

$$
\(A C \leq A B+B C=18\)
$$

- Comparing Quantity A (diagonal $\(A C\)$ ) with Quantity B ( $\(9 \sqrt{2}\)$, approximately \(12.73\) ):
- The diagonal $A C$ can be as small as the difference of the two sides (if the parallelogram is very "flat") or as large as the sum of the two sides (if it's more like a rectangle or square).
- Since $\(A C \leq 18\)$, it could be bigger or smaller than $\(9 \sqrt{2} \approx 12.73\)$.
- So, depending on the shape, Quantity A can be either less than, equal to, or greater than Quantity B.

Conclusion: Without specific side lengths or angle info, the relationship between Quantity A and Quantity B cannot be determined.