Answer: The focal point of the mirror is greater tahn the 18 feet.
Explanation:
Concave mirror only forms the virtual image when an object is placed between the focal length and principle axis of the concave mirror.
The image generated by the mirror was virtual image of the flower which appeared behind the mirror. The flower was kept at the distance of 18 feet away from the mirror which means that the focal point of the concave mirror is greater than the 18 feet.
