`100 ml` of water at `20^(@)C` and `100 ml` of water at `40^(@)C` are mixed in calorimeter until

`100 ml` of water at `20^(@)C` and `100 ml` of water at `40^(@)C` are mixed in calorimeter until constant temperature reached. Now temperature of the mixture is `28^(@)C`. Water equivalent of calorimeter is