code: def distance(a, b):
      
      R = 3963  # radius of Earth (miles)
      lat1, lon1 = math.radians(a[0]), math.radians(a[1])
      lat2, lon2 = math.radians(b[0]), math.radians(b[1])
      return math.acos(math.sin(lat1) * math.sin(lat2) +
                       math.cos(lat1) * math.cos(lat2) * math.cos(lon1 - lon2)) * R
docs: Calculates distance between two latitude-longitude coordinates.