"The existence of a widespread customary law was noticed by early European visitors to Africa, in particular by the Portuguese. Traders enjoyed, for example, the protection of law for the unwritten contracts, based on oaths and 'medicine', which they made with the local inhabitants. Conversely, these European traders resented the application of West African law under which the property of a dead colleague, or their ships gone aground along the coast, were forfeit to the local ruler. Thus it seems that customary law, this 'unity in diversity', provided a bond between the different states and peoples of West Africa, and a form of international law by which their relations with each other could be regulated." - Robert Smith, 'Peace and palaver: International relations in pre-colonial West Africa' Journal of African History (1973).

Based on the quote above, explain how African customary law shaped the following practises in pre-colonial Africa:

a) The appointment of ambassadors

b) The immunity for the persons and possessions of diplomats

c) Agreement on peace treaties