What is the \(f\) - number of lens in Problem 3.5 with light

(a) from the left and

(b) from the right?

Problem 3.5

Ten-inch focal length lens forms an image of a telephone pole that is 200 ft away (from its first principal point). Where is the image located
(a) with respect to the focal point of the lens and

(b) with respect to the second principal point?