Two hikers, Alex and Emma, start hiking towards each other from two different points, Point X and Point Y, which are 80 kilometres apart. Alex hikes at a speed of 18 km/h for the first 36 kilometres, and then hikes at a speed of 13 km/h for the remaining distance. Emma hikes at a constant speed of 12 km/h throughout the journey. How long will it take for Alex and Emma to meet each other?