Answer
See explanation.
Work Step by Step
The copper rod is a much better conductor than the building materials, so the current will primarily choose that path to ground rather than to pass through the building.
The end of the rod should be rounded because the electric field is stronger near surfaces that are more curved rather than flat. This effect first ionizes the air near the end of the rod, making it the most likely place to be struck by lightning (rather than the building).
