Task: Question Answering
Input (English): Problem: matt and peter can do together a piece of work in 20 days . after they have worked together for 10 days matt stops and peter completes the remaining work in 10 days . in how many days peter complete the work separately . 
Options: a ) 21 , b ) 20 , c ) 22 , d ) 23 , e ) 24
Output (English): b