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'.

Input: Consider Input: Problem: annie and sam set out together on bicycles traveling at 15 and 12 km per hour respectively . after 40 minutes , annie stops to fix a flat tire . if it takes annie 30 minutes to fix the flat tire and sam continues to ride during this time , how many minutes will it take annie to catch up with sam assuming that annie resumes riding at 15 km per hour ? 
Options: a ) 20 , b ) 40 , c ) 60 , d ) 80 , e ) 100

Output: d


Input: Consider 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']

Output: a


Input: Consider Input: Problem: a man swims downstream 28 km and upstream 12 km taking 2 hours each time , what is the speed of the man in still water ? 
Options: a ) 10 , b ) 8 , c ) 5 , d ) 2 , e ) 4


Output: a