Task: Question Answering
Input (English): Problem: the average age of 39 students in a group is 14 years . when teacher ' s age is included to it , the average increases by one . what is the teacher ' s age in years ? 
Options: a ) 35 years , b ) 45 years , c ) 51 years , d ) 54 years , e ) none of these
Output (English): d