Calculate the separation of the lenses?

An astronomical telescope having an objective of focal length 100cm and an eyepiece of focal length 10cm is used in normal adjustment, calculate the separation of the lenses

A. 0.10m
B. 0.90cm
C. 1.10m
D. 1.80m
E. 2.20m

Correct Answer:

Option C = 1.10m