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: a and b together do a work in 20 days . b and c together in 15 days and c and a in 12 days . so a , b and c together finish same work in how many days ? 
Options: a ) 12 , b ) 15 , c ) 8 , d ) 10 , e ) 11

Output: d


Input: Consider Input: Problem: in what time will a railway train 60 m long moving at the rate of 36 kmph pass a telegraph post on its way ? 
Options: a ) 2 , b ) 7 , c ) 8 , d ) 6 , e ) 9

Output: d


Input: Consider Input: Problem: a boat running up stram takes 4 hours to cover a certain distance , while it takes 8 hours to cover the same distance running down stream . what is the ratio between the speed of the boat and the speed of water current respectively ? 
Options: a ) 2 : 3 , b ) 5 : 6 , c ) 4 : 5 , d ) 3 : 1 , e ) 8 : 1


Output: d