sentence1: 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
sentence2: Two birds start flying simultaneously towards one another , the first leaving from West - Town at a speed of 3 kilometers per minute and the second bird , leaving from East - Town , at a speed of 1 kilometers per minute