How to assassinate the target, professional assassin Arlanda undoubtedly had the most say.
She pointed at the upper corridor of the West Tower of the Lord's Mansion and said, "This place leads to the top platform of the Lord's Mansion, where airships can dock at the air berths. Anderson placed those Mages in the West Tower, probably so that they can quickly enter the airships if needed. There aren't too many obstacles along this route, which makes it perfect for sniping. This arrow tower here is a very good sniper point. From a commanding height, as long as they enter the corridor, there are almost no covers available for use."
Chui Chui, based on Arlanda's description, zoomed in on the West Tower, the corridor, and the air berth, and marked the shooting range of the arrow tower. Professional as she was, Arlanda's chosen sniper spot indeed covered the entire stretch of the route within sniping range.
