An x-ray field at a point P contains 7.5 X 10' photons/m'-sec-keV, uniformly distributed from 10 to 100 keV. a) What is the photon flux density at P? b) What would be the photon fluence in one hour? c) What is the corresponding energy fluence, in J/m² and erg/cm²? d) Calculate the exposure in C/kg.