$${\frac{dm}{dt} = \frac{dE/dt}{c^2} = \frac{3,4 \times 10^9\, \mathrm{W}}{(3,00 \times 10^8\, \mathrm{m/s})^2} \\ = 3,8 \times 10^{-8}\, \mathrm{kg/s} = \underline{\underline{3,3\, \text{g/päevas}}}}$$