Before revision:  This paper aims at solving this kind of the optimal problems, that is, working out the optimal control policy of the insurance company , in particular, exact minimum dividend barrier, and finding the optimal return function associated with the optimal policy .
After revision:  This paper aims at solving this kind of the optimal problems, that is, deriving the optimal retention ratio,dividend payout level, optimal return function and optimal control policy of the insurance company , in particular, exact minimum dividend barrier, and finding the optimal return function associated with the optimal policy .