Supposed that at t=0, we connect an uncharged 10μF capacitor to a charging circuit consisting of a 2500V voltage source in series with a 2MΩ resistance. At t=40s, the capacitor is disconnected from the charging circuit and connected in parallel with a 5MΩ resistor. Determine the voltage cross the capacitor at t=40s and at t=100s. (Hint: You may find it convenient to redefine the time variable to be t'=t-40 for the discharging interval so that the discharge starts a t'=0.)