We know that - VM=VCl - R1=1000.0 Ω - IM=0 - VNa=61 mV - VK=-88 mV - VCl=-71 mV Question is: what is R2? I've written according to Kirchhoff's second law that (1) VM + VNa - R1INa = 0 and (2) VM - VK - R2IK = 0. We can also calculate that ICl=0. With these equations and according to Kirchhoff's first law we can solve (using absolute values) that R2=128.789 Ω that is a correct answer. The problem is that I wonder why VM is always positive? Shouldn't it be negative in the first equation? If we go through capacitor and then Na-part of the circuit, the capacitor will have a negative charge at the bottom and a positive charge at the top because so has VNa. (Instead, if we continue to K or Cl part of the circuit, the capacitor will have a positive charge at the bottom and a negative at the top.) So the first equation would be -VM + VNa - R1INa = 0 but then we get an incorrect answer. I see that I must have misunderstood something but I don't know what is it.