My SQL Solution :

-- ---> manhatten distance Formula = |x1-x2|+|y1-y2| -- as per question a = x1, b = y1, c = x2, d = y2 --abs() = return a non negative value

select round(abs(min(lat_n)-max(lat_n)) + abs(min(long_w)-max(long_w)), 4) from station `