Read this and answer the question. If the question is unanswerable, say "unanswerable".

The development of writing enabled knowledge to be stored and communicated across generations with much greater fidelity. Combined with the development of agriculture, which allowed for a surplus of food, it became possible for early civilizations to develop, because more time and effort could be devoted to tasks (other than food production) than hunter-gatherers or early subsistence farmers had available. This surplus allowed a community to support individuals who did things other than work towards bare survival. These other tasks included systematic studies of nature, study of written information gathered and recorded by others, and often of adding to that body of information.

Having a surplus of food allowed farmers and hunter-gatherers to spend less time working on what?
food production