If a Camera Lens Lets in an Amount of Light $I$

Multiple Choice

If a camera lens lets in an amount of light $I$ when it is set to $f / 4$ , then how much light will it let in when it is set to $f / 8$ ?

A) $I / 4$
B) $4 I$
C) $16 I$
D) $I / 2$
E) $2 I$