Task: Question Answering
Input (English): Problem: the speed of a railway engine is 84 km per hour when no compartment is attached , and the reduction in speed is directly proportional to the square root of the number of compartments attached . if the speed of the train carried by this engine is 24 km per hour when 9 compartments are attached , the maximum number of compartments that can be carried by the engine is : 
Options: a ) 19 , b ) 18 , c ) 16 , d ) 17 , e ) 14
Output (English): d