You’re all wrong if it’s 3x4 then a a border of 12 units would take up the entire area so it wouldn’t be a border anymore. The correct answer isn’t there, none of the above.
Nope. 12 SQUARE units would cover the entire area. 12 units would not unless their width was the same as the quilting patches. Even so, a border extends outwards so it doesn’t matter how wide the border is.