Karen has two children, a boy named Dave and a girl Nancy. They are both lovely. And the boy loves his little sister very much for he thinks he must protect her. Yet, the little girl got a serious illness one day and needed some blood. But the hospital couldn't find the same type of blood for the girl. Karen knew her both children have the same type of blood. So she asked her son, "Would you like to give your blood to your sister?"
Dave agreed at once. After transferring his blood, the boy asked his mother, "Mom, how long can I live from now on?" Karen understood her son had thought he would die soon after he lost some of his blood. So she said to him, "Don't worry, my son. You won't die if you lose a little blood."
"Really? How long can I live?" the boy asked his mother again. "I think you can live to be 100 years old," smiled his mother. The boy lifted his arms and said happily, "Well, please give half of my blood to my little sister! Then both of us can live 50 years!"
