Halliday, Resnick & Walker — Relativity: Problem 37

37 Quasars are thought to be the nuclei of active galaxies in the early stages of their formation. If a quasar radiates energy at the rate of $2.00 \times 10^{41} \text{ W}$, at what rate is the mass of this quasar being reduced to supply this energy? Express your answer in solar mass units per year, where one solar mass unit ($1 \text{ smu} = 2.0 \times 10^{30} \text{ kg}$) is the mass of our Sun.