Two identical pulses each of magnitude 12 V and width 2 s are incident at t =

Two identical pulses each of magnitude 12 V and width 2 μs are incident at t = 0 on a lossless transmission line of length 400 m terminated with a load. If the two pulses are separated 3 μs and μ = 2 x 10⁸ m/s, when does the contribution to V_L (ℓ, t) by the second pulse start overlapping that of the first?
(a) t = 0.5 μs
(b) t = 2 μs
(c) t = 5 μs
(d) t = 5.5 μs
(e) t = 6 μs