If BC=2, AB=2 and B'C'=4 then compute A'B'

Question

the picture is a box starting lower left, the letters go A',B',C',P' clockwise. Then there are lines that go down to form a tip. In the middle going down those lines its just A,B,C,P. Then where it meets at the point it is A",B",C",P". I tried tinyurl but it wont let me upload the picture!