In this task, you need to answer the given multiple-choice question on the physics. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.

Example Input: Problem: the cyclist going at a constant rate of 20 miles per hour is passed by a motor - cyclist traveling in the same direction along the same path at 60 miles per hour . the motor - cyclist stops to wait for the cyclist 10 minutes after passing her , while the cyclist continues to travel at constant rate , how many minutes must the motor - cyclist wait until the cyclist catches up ? 
Options: a ) 10 , b ) 20 , c ) 25 , d ) 30 , e ) 40
Example Output: b

Example Input: Problem: 45 men working 8 hours per day dig 40 m deep . how many extra men should be put to dig to a depth of 50 m working 6 hours per day ? 
Options: a ) 10 , b ) 20 , c ) 30 , d ) 40 , e ) 50
Example Output: c

Example Input: Problem: machine a can process 6000 envelopes in 3 hours . machines b and c working together but independently can process the same number of envelopes in 2.5 hours . if machines a and c working together but independently process 3000 envelopes in 1 hour , then how many hours would it take machine b to process 7000 envelopes . 
Options: a ) 2 , b ) 3 , c ) 4 , d ) 5 , e ) 60 / 7
Example Output:
d