An object is standing in front of a convex mirror. The image is reflected 3 feet behind the mirror which has a focal length of 15 feet. The image is 5 ft tall. How tall is the object? Express your answer with at least two decimal places. Note: When entering your final answer in the input box, include the sign if the answer involves a negative sign e.g. -14.22. If positive, there's no need to include the sign