Answer:

Introduction:
Ibn Battuta was a famous Moroccan traveler and explorer who visited many countries in the 14th century. He is known for his detailed travelogue, Rihla, which describes his experiences and observations during his travels.

Efficiency of Postal System:
During his travels, Ibn Battuta was amazed by the efficiency of the postal system in the Delhi Sultanate, which was ruled by Muhammad Bin Tughluq.

Postal System in Delhi Sultanate:
The postal system in the Delhi Sultanate was called the "Dak Chowki" and it was used to send messages and letters across the vast empire. The system was well-organized and had a network of post offices and horse riders who carried the mail.

Ibn Battuta's Observation:
Ibn Battuta was impressed by the speed and efficiency of the postal system. He wrote in his travelogue that "the Sultan has established innumerable post-houses and has appointed able and experienced officers to take charge of them. The horses are kept in readiness, and the dispatch of letters is so rapid that in the space of a single day and night a letter can be carried from one end of the kingdom to the other."

Conclusion:
Ibn Battuta's observation of the efficiency of the postal system in the Delhi Sultanate is a testament to the advanced state of communication and transportation in medieval India. The Dak Chowki system was an important tool for the administration and communication in the empire and it helped to maintain the unity and cohesion of the vast empire.