Çözüldü Electric Circuits with Resistor and Capacitor

Test adaptation from Missouri University of Science and Technology:

If a capacitor of 6 µF capacitance has been charged so that the potential difference between its plates is 80 Volts, and is connected to a 10 kΩ resistor in a series circuit through a switch initially off, and later the switch is closed so the capacitor begins to discharge, how long in milliseconds does it take the charge to decrease to one third of its maximum value?

A) 20·ln(2)
B) 30·e
C) 240 / e
D) 60·ln(3)
E) 180


https://i.ibb.co/fHFQW59/mst.png
https://web.mst.edu/~vojtaa/phys2145/oldexams/p2145s18_test2_solved.pdf
(The last question, parts a and e)