How much did robertson mumford purchase his slave for?

Robertson Mumford purchased his slave for four gallons of rum and a piece of calico cloth.

Explanation:

Venture Smith was held captive at the age of six and a half in West Africa in 1739. He was then taken to Ghana and was bought by Robertson Mumford, who paid four gallons of rum and some calico cloth for him.  His birth name was Broteer Furro (1729-1805). He spent his life in Rhode Island, Connecticut, Mumford's home, where he finally bought his freedom. His autobiography, "A Narrative of the Life and Adventures of Venture, a Native of Africa: But Resident above Sixty Years in the United States of America, Related by Himself" depicts the African American voice of the slave.

Venture Smith. Venture Smith (Birth name: Broteer) (c. 1729 – 1805) was captured when he was a 6 and a half-year-old boy in West Africa and was taken to Anomabo on the Gold Coast (today Ghana) to be sold as a slave. As an adult in Rhode Island (Connecticut), he purchased his freedom and that of his family.