A. 20 m
Feedback A can give B 10 m
In a 100 m race, while A starts from the starting point, B starts 10 meters ahead from the same starting point at the same time.
A can give C 28 mIn a 100 m race, while A starts from the starting point, C starts 28 meters ahead from the same starting point at the same time.
i.e., in a 100-10=90 m race, B can give C 28-10=18 m
In a 100 m race, B can give C 18/90×100 = 20 m