Task: Question Answering
Input (English): Problem: machine a takes 100 hours to complete a certain job and starts that job at 6 am . after ten hour of working alone , machine a is joined by machine b and together they complete the job at 6 pm . how long would it have taken machine b to complete the job if it had worked alone for the entire job ? 
Options: a ) 24.65 , b ) 22.27 , c ) 2.273 , d ) 11.62 , e ) 21.13
Output (English): c