1. The problem statement, all variables and given/known data In the circuit below (drew it the best I can) the switch is opened, how much time elapses before the capacitor loses half of its initial stored energy. 2. Relevant equations q(t) = Qe-t/RC U = q2/2C 3. The attempt at a solution So first thing I did was I set (1/2)Q2/2C = q2/2C then i replaced q2 for Q2e-2t/RC so I get (1/2)Q2/2C = Q2e-2t/RC/2C I cancel out the like terms and I am left with 1/2 = e-2t/RC I than get rid of the e so I get ln(1/2) =-2t/RC then i get -ln(2) = -2t/RC getting me t = RCln(2)/2 and now this is were i got confused I know C = 200E-6 F but i don't know what R is suppose to be, I think it is suppose to be 90Ω since the 30Ω and the 60Ω resistors connect together at where the capacitor is.