grandma and son

A boy and his grandma were walking down a lane. The boy sees a five pound note on the floor and asks his grandma can I pick it up, but grandma says no! you should never pick up fallen things. They walked a little further and the boy sees fifty pounds in a wallet on the floor and asks his grandma, again can I pick it up, but the grandma says no! you should never pick up fallen stuff even if it costs more than one thousand pounds. They continue walking and after a while the grandma falls down and asks the grandson for help and the grandson replies no! even if the fallen thing costs more than one thousand pounds, you should never pick it up.