Currency arbitrage

Today, the Hong Kong $ is offered at $0\mathrm{.}09598$ euros in Rome, and the $$ is offered at $0\mathrm{.}06656$ HK$ in the official forex screens. At the same time, we found that one $$ is bid $($sold & bought$)$ at $0\mathrm{.}006693$ euros in an unregulated grey market. If you were an astute trader, what would you do to earn a little bit of money without barely assuming risks?