The correct answer is: "Muslim merchants".
The Dyula were an ethnic gruoup that inhabited the Mali Empire. They were sucessful merchants who developed trade communities in Mali and also in other Western African territories such as Cote d'Ivoire, Ghana or Burkina Faso.
Moreover, the Dyula constituted a Muslim minority in non-Muslim territories, this is why they developed theological principles and manners of integrating the practice of their religion and their business activities in such territories. They were essential contributors to the peaceful expansion of Islam in West Africa during the 14th century.