The Objective Lens of the Yerkes Telescope (The Largest Functioning

Multiple Choice

The objective lens of the Yerkes telescope (the largest functioning refracting telescope in the world) has a focal length of 19.4 m.If its eyepiece has a focal length of 2.5 cm, what is the magnitude of its magnification?

A) 7.8
B) 13
C) 130
D) 780
E) cannot be calculated without knowing the length of the telescope