Data envelopment analysis for ambulance services of different service providers in urban and rural areas in Ministry of Health Malaysia by Mohd Hassan, Nor Zam Azihan, Bahari, Mohd Shahri, Aminuddin, Farhana, Mohd Nor Sham Kunusagaran, Mohd Shaiful Jefri, Zaimi, Nur Amalina, Mohd Hanafiah, Ainul Nadziha, Kamarudin, Fakarudin