Mr. and Mrs. Ramesh and their son Ravi would like to cross a river. The only way to cross the river is by using the boat of Mr.Nimal. He will not allow anybody else to row his boat and will take only one passenger at a time. Ravi is only a little boy, so he cannot be left alone on the river bank. Which one of the following is not possible for a successful crossing of the river by the Ramesh family?