Compare a 6th-magnitude star with an 11th-magnitude star in brightness. Which is brighter, and by how many times?
a) The 6th-magnitude star is brighter by 625 times.
b) The 11th-magnitude star is brighter by 25 times.
c) The 6th-magnitude star is brighter by 5 times.
d) The 11th-magnitude star is brighter by 125 times.