Q1:

V_R at t < T, t = ∞

At t = 0, C₁, C₂, C₃ acts as short. ∴ entire voltage will appear cross R. At t increases the voltage across the resistance decrease exponentially. T = RC_net = 10 x 2.5 x 10^-6 = 25 μ sec Initial voltage V_R = V₀e^-t/RC at t = 0 = 100 = 100 e^-t/25x10-6 V. V_R = 100 e^-40x104t V. At t = ∞, V_R = 0 The charge C₀ will be distributed in C₁, C₂, C₃ and no current will flow.