A long line responds after a finite source-bound delay. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
A line delay is length divided by signal speed
A 12 meter line with signal speed 3 meters per second has a checked travel time.
t=12m÷3m/s
The step reaches the load after the checked delay
The one-way delay is 4 seconds, so the load cannot respond instantly.