Writing -How does Williams link the use of slave labour

How does Williams link the use of slave labour with the development of capitalism? Why was slavery and not ‘free labour’ the answer to the production of staples like tobacco and sugar during the early stages of colonial development (in the US and caribbean)? What do Conrad’s refrences to “light” and “darkness” represent?. How does conrad represent the effects of slavery? in what ways do you think conrad questions and challenges notions that Europe was bringing progress to Africa?