Mathematics

Problem

Two stars are the same distance from earth, and their apparent brightnesses are

9.0 \times 10^{-12}\,\mathrm{W\,m^{-2}}

(star A) and

3.0 \times 10^{-13}\,\mathrm{W\,m^{-2}}

(star B). Calculate the ratio of the luminosity of star A to that of star B.