Task: Question Answering
Input (English): Problem: the distance between west - town to east - town is 20 kilometers . two birds start flying simultaneously towards one another , the first leaving from west - town at a speed of 4 kilometers per minute and the second bird , leaving from east - town , at a speed of 1 kilometers per minute . what will be the distance , in kilometers , between the meeting point and west - town ? 
Options: a ) 3 . , b ) 7 . , c ) 10 . , d ) 16 . , e ) 15 .
Output (English): d