Nikkei hits new 5-1/2-yr high on weak yen; financials, exporters lead

* Volume highest in 5 weeks * With USD/JPY assumption at 100, profits to rise 28 pct - analyst * Nikkei may reach 15,000 this week - brokers By Tomo Uetake TOKYO, May 13 (Reuters) - Japan's Nikkei share average surged to a fresh 5-1/2-year high on Monday as the weakening yen further bolstered exporters, while brokerage shares attracted buyers who see growing volume bringing in much more fee income. The benchmark Nikkei rose 1.2 percent to 14,782.21, its highest closing leve