Solve a problem for non-chicken peeps!

As non-chicken people we are having a discussion and need some clarification, so I thought you kind folk might be able to help.a) Given that hens lay automatically once they are mature enough, do they stop laying once they lay a fertilised egg? b)Do they lay a whole clutch of fertilised eggs in one go or does each egg have to be fertilised individually? C) Does the hen know which eggs are fertilised at the point of lay or do they try to sit on them all?

Thanks Aunty, that helps a lot! Puts a stop to the arguments - I knew I could always rely on the forum!