Three squares ABB1B2,BCC1C2,CAA1A2 are constructed in the exterior of a triangle ABC. In the exterior of these squares, another three squares A1B2B3B4,B1C2C3C4,C1A2A3A4 are constructed. Prove that the area of a triangle with sides C3A4,A3B4,B3C4 is 16 times the area of △ABC.