Hong Kong billionaire Li Ka-Shing has made a $4.5 billion bid for Australian energy giant Duet Group. The Australian government rejected Ka-Shing's initial bid in August for a majority stake in state-owned power network Ausgrid, citing security reasons. Duet’s biggest shareholder with 15.6 percent is the education sector pension fund UniSuper. The company's second largest shareholder is Lazard Asset Management Pacific Co., a privately owned investment firm.