In the analysis: First we had to determine the injection function, which usually is taken as an unknown and found after extensive simulation. But in this case we postulated that it represents injection (based on the time behaviors). The Yohkoh HXT count rate is in this form. We assume a single power law for the photon spectrum, and simulate the observed count rate using the response function P_I to derive the A and gamma factors. Once we get these A and gamma factors we can, using Brown’s formula, reconstruct the electron spectrum at any time and energy (of course under a single power law assumption). As a  result we found the injection spectrum in a time-dependent form not only amplitude but also the spectral slope. The spectral slope change itself could make the inversion problem difficult to solve.