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: if 20 typists can type 48 letters in 20 minutes , then how many letters will 30 typists working at the same rate complete in 1 hour ? 
Options: a ) 63 , b ) 72 , c ) 144 , d ) 216 , e ) 400

Output: d


Input: Consider Input: Problem: a train , 800 meter long is running with a speed of 78 km / hr . it crosses a tunnel in 1 minute . what is the length of the tunnel ? 
Options: a ) 650 meter , b ) 555 meter , c ) 500 meter , d ) 458 meter , e ) none of these

Output: c


Input: Consider Input: Problem: two persons a and b can complete a piece of work in 30 days and 45 days respectively . if they work together , what part of the work will be completed in 7 days ? 
Options: a ) 2 / 5 , b ) 7 / 18 , c ) 1 / 4 , d ) 1 / 9 , e ) 2 / 6


Output: b