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 can do a work in 12 days , b and c in 15 days , c and a in 20 days . if a , b and c work together , they will complete the work in : 
Options: a ) 5 days , b ) 7 5 / 6 days , c ) 10 days , d ) 15 2 / 3 days , e ) none of these

Output: c


Input: Consider Input: Problem: walking with 5 / 4 of my usual speed , i miss the bus by 5 minutes . what is my usual time ? 
Options: a ) 18 , b ) 19 , c ) 20 , d ) 22 , e ) 24

Output: c


Input: Consider Input: Problem: a train running at the speed of 180 km / hr crosses a pole in 36 seconds . what is the length of the train ? 
Options: a ) 450 m , b ) 500 m , c ) 550 m , d ) 600 m , e ) 650 m


Output: d