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: a hollow iron pipe is 21 cm long and its external diameter is 8 cm . if the thickness of the pipe is 1 cm and iron weights 8 g / cm cube , then find the weight of the pipe .
Options: ['a ) 3.696 kg', 'b ) 3.686 kg', 'c ) 2.696 kg', 'd ) 2.686 kg', 'e ) none of these']
Example Output: a

Example Input: Problem: ajay can walk 6 km in 1 hour . in how many hours he can walk 70 km ?
Options: a ) 5 hrs , b ) 11.6 hrs , c ) 15.6 hrs , d ) 20.1 hrs , e ) 30 hrs
Example Output: b

Example Input: Problem: two trains each 150 m in length each , are running on two parallel lines in opposite directions . if one goes at the speed of 95 km / h while the other travels at 85 km / h . how long will it take for them to pass each other completely .
Options: a ) 25 sec , b ) 23 sec , c ) 34 sec , d ) 22 sec , e ) 6 sec
Example Output:
e