Answer:
It is less expensive to find safe areas than to change all the doors and windows.
Step-by-step explanation:
Finding safe places against tornadoes is as efficient as using special tornado-resistant doors and windows, and finding a safe place is cheaper and most public schools don't have a big enough budget to put special doors and windows around the world. because this kind of material is expensive. For this reason, group 1, shown in the question above had a more efficient idea than group 2.