A race consists of three stretches $A, B$ and $C$ of $2$kms length each. The mode of coverage, and maximum and minimum of speeds possible in each stretch are:
||Minimum Speed (Km/h)
||Maximum Speed (Km/h)
Speed in a given stretch remains constant. The previous record was ten minutes to complete the race.
Mr. Tortoise travelled in the overall race at an average speed of $20$ km/h. However, his average speed over the first two stretches combined was four times that over the last stretch. What was his speed over the last stretch?
- $15$ km/h
- $10$ km/h
- $20$ km/h
- Cannot be determined