How Do You Calculate Capacitance in a Series RC Circuit?

[UnseenAngels07]

the problem is a series combination of 12k resistor and an unknown capacitor is connected to a 13 volt battery. One second after the circuit is completed, the voltage across the capacitor is 8v. Determine the capacitance of the capacitor.

 

[mukundpa]

This is the problem related of charging a capacitor.
The equation for the charge on the capacitor as a function of time is

\q = CV \left( 1 - e^\ -t/CR \right)