What are the three major reasons on how capitalism and slavery are connected

Plz help

Capitalism is an economic system based on the private ownership of the means of production and their operation for profit. Central characteristics of capitalism include capital accumulation, competitive markets, a price system, private property and the recognition of property rights, voluntary exchange and wage labor.

Slaveholders, the cliometricians argued, were capitalists for two reasons. First, their slaves were hugely productive and earned them a great profit. Second, they were in tune with the market and responded to its mechanisms. With these arguments, the cliometricians stand out as a notable group that considers slavery a form of capitalism.

I can find two of the three sorry

What book is this referring to?