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'.

Ex 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']

Ex Output:
a


Ex 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

Ex Output:
c


Ex Input:
Problem: a monkey ascends a greased pole 17 metres high . he ascends 2 metres in first minute and slips down 1 metre in the alternate minute . in which minute , he reaches the top ? 
Options: a ) 31 st , b ) 22 nd , c ) 23 rd , d ) 24 th , e ) none of these

Ex Output:

a