The statements in the question can be reformulated as follows:
If A covers 400 m, B covers 395 m.
If B covers 400 m, C covers 396 m.
If D covers 400 m, C covers 384 m.
Therefore, if B covers 395 m, then C will cover,
×395 = 391.05m
Again, If C covers 391.05 m, then D will cover
× 391.05 = 407.34 m
Thus, if A and D run over 400 m, then D wins by 7.3 m.