  This paper studies the optimal dividend problem with capital injection under
the constraint that the cumulative dividend strategy is absolutely continuous.
We consider an open problem of the general spectrally negative case and derive
the optimal solution explicitly using the fluctuation identities of the
refracted-reflected L\'evy process. The optimal strategy as well as the value
function are concisely written in terms of the scale function. Numerical
results are also provided to confirm the analytical conclusions.
