When comparing the tumor size on the chest x-ray projection radiography, caution must be used

When comparing the tumor size on the chest x-ray projection radiography, caution must be used. Suppose a patient has two focal tumors of the same actual size in the lung, one closer to the front and the other closer to the back of the body. Suppose the front focal tumor is distant to the x-ray source by 2 meters. On the radiography film, the fronttumor measures 10 mm, the back-tumor measures 9 mm. Calculate the distance between the two tumors. Drawing a figure is helpful.