Chapter 14, Problem 14.74P

$18$-Annulene shows two signals in its ${}^1\text{H}\text{NMR}$ spectrum, one at $8.9\left(12\text{H}\right)$ and one at $-1.8\left(6\text{H}\right)\text{ppm}$. Using a similar argument to that offered f or the chemical shift of benzene protons, explain why both shielded and deshielded values are observed for $18$-annulene.