A race course is 400 m long. AA and BB run a race and AA wins by 5m. BB and CC run over the same course and BB win by 4m. CC and DD run over it and DD wins by 16m. If AA and DD run over it, then who would win and by how much?	Choose the correct choice from the following
A) 7.1 m  B) 7.2 m  C) 8 m  D) 9 m  E) 11 m

Rationale: if aa covers 400 m , bb covers 395 m if bb covers 400 m , cc covers 396 m if dd covers 400 m , cc covers 384 m now if bb covers 395 m , then cc will cover 396400 × 395 = 391.05396400 × 395 = 391.05 m if cc covers 391.05 m , then dd will cover 400384 × 391.05 = 407.24400384 × 391.05 = 407.24 if aa and dd run over 400 m , then dd win by 7.2 m option b
Answer: B