You Have a Choice Between Two Lenses of Focal Lengths

Multiple Choice

You have a choice between two lenses of focal lengths f_a and f_b = 2 f_a to use as objective lens in building a refracting telescope. If the magnification you obtain using lens A is M_a, what will be the magnification when using lens B?

A) M_b = 2 M_a
B) M_b = 4 M_a
C) M_b = 8 M_a
D) M_b = M_a /4
E) M_b = M_a /2