Problem 4. (10 Points) A capacitor with capacitance
C=10\mu Fis fully charged by connecting to a battery with emf
V=20V. After that, it is disconnected from the battery and connected to a resistor with resistance
R=10MOhm. (a) At what time will the capacitor charge be at
80%of its initial value? (b) What will be the amount of charge at the capacitor at that time?