After taking a radiograph exposure of a patient's abdomen at a 40 cm focal-film distance, you repeat the exposure using a horizontal beam technique at an 80 cm focal-film distance. What settings should you use to obtain the same radiographic density?
a) kVp=60, mAs=4
b) kVp=70, mAs=2
c) kVp=80, mAs=2
d) kVp=90, mAs=1
