Commercial layers can lay between 240-310 eggs in a lifetime.
However, the number of eggs laid depends on several other factors including the feeding and the general environment in which the chicken are kept.
For example, loud noise near the chicken houses can affect the egg laying process. Poor feeding can reduce egg production, just like the temperature in the chicken house and diseases like newcastle.
You can tell that a chicken is laying eggs if its comb is brick red, the feathers are shiny and the vent is wide and can take three fingers spread across it.