On a Night When a Human Eye Can See a Fourth

Multiple Choice

On a night when a human eye can see a fourth magnitude star, a 60mm telescope, with 100× the surface area as our pupil, would be able to just barely detect

A) eleventh magnitude Tethys, Saturn's second largest moon.
B) seventh magnitude Titan, Saturn's largest moon.
C) ninth magnitude Barnard's Star.
D) eighth magnitude Uranus.
E) thirteenth magnitude Pluto.