exchange of goods exists because there's a demand for things. their type, the conditions of their production and the manner of their exchange is something else.
you can start right on page 26 of das kapital
https://www.marxists.org/archive/marx/works/download/epub/capital-v1.epub
i find that unfiltered black coffee has a lot of body. 2 heaped teaspoons of ground coffee, 200ish mls of boiling water. let it soak, then stir carefully. the coffee sinks to the bottom leaving you with rich flavorful goodness.