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 can do a piece of work in 80 days and b in 100 days . they work together for 20 days and then b goes away . in how many days will a finish the remaining work ?
Options: a ) 33 days , b ) 44 days , c ) 55 days , d ) 42 days , e ) 32 days

Ex Output:
b

Ex Input:
Problem: today mary ' s father is 4 times as old as mary . 3 years ago , he was 5 times as old . how old is mary today ?
Options: a ) 6 , b ) 8 , c ) 10 , d ) 12 , e ) 14

Ex Output:
d

Ex Input:
Problem: 20 men can dig a tunnel in 30 days . if after 10 days , 20 more men are deployed to dig the tunnel , how many more days it will take to dig the whole tunnel ?
Options: a ) 10 , b ) 15 , c ) 20 , d ) 25 , e ) 30

Ex Output:
a