Finding resistane and current non-ohmic

[Eagle's Wings]

Homework Statement

A 10.0-μF capacitor is charged by a 10.0-V battery through a resistance R. The capacitor reaches a potential difference of 4.00 V at the instant 3.00 seconds after charging begins
1.) Find R
2.) Find the current at t=3.00 seconds after charging begins.

Homework Equations

i=\frac{dq}{dt}=-\frac{CV_{ab}}{RC}e^{-t/RC}

The Attempt at a Solution

so obviously I know how to find current but I need to find resistance and I cannot use R=V/I because it is non-ohmic! what do I do?

 

[gneill]

Find the time constant $\tau = RC$. You know C...

 

[Eagle's Wings]

why am i using time constant?

 

[gneill]

why am i using time constant?

Read the question carefully. Some information you're given involves time. If you can find the time constant RC and you already know C then...