Answer:
0.046 m
Step-by-step explanation:
The lens equation states that:

where
f is the focal length
p is the distance of the object from the lens
q is the distance of the image from the lens
For this problem, we have
p = 4.0 m (distance of Betty and Ahmed from the lens)
f = 0.045 m (focal length of the lens, which is positive since it is a converging lens)
So we can re-arrange the formula to find q
