A 400 F capacitor is charged using a 20 V battery. It is connected across the ends

A 400 μF capacitor is charged using a 20 V battery. It is connected across the ends of a 600 Ω resistor with 20 V potential difference across its plates.
a. Calculate the charge stored on the capacitor.
b. Calculate the time constant for the discharging circuit.
c. Calculate the time it takes the charge on the capacitor to fall to 2.0 mC.
d. State the potential difference across the plates when the charge has fallen to 2.0 mC.