Physics Halp

Please help, I've got through almost all of my physics paper for the holidays and I'm stuck on this question because my teacher made us teach the entire Astrophysics section to ourselves so no one in my class knows how to do this -

7)
a) In a particular binary system, star A has apparent brightness 8.0 x 10^-13 W m-2 and star B has apparent brightness 2.0 x 10^-14 W m-2.

i) Explain how it is possible to deduce that star A has a higher luminosity than star B.

ii) The surface area of star B is 10,000 times smaller than that of star A. Calculate the ratio

surface temperature of star B / surface area of star A