It was Jimmy's fifth birthday, He got many presents from his family, and one of them was a beautiful big drum (鼓). 'Who gave him that thing?' Jimmy's father asked when he saw it. 'His grandfather did,' answered Jimmy's mother. Jimmy liked his drum very much. He made a terrible noise with it, but his mother did not mind. His father was working during the day, and Jimmy was in bed when he got home in the evening, so he did not hear the noise. But one of the neighbors did not like the noise, so one morning, she took a sharp(锋利) knife and went to Jimmy's house while he was playing his dram. She said to him, 'Hello, Jimmy. Do you know there's something very nice inside your drum? Here is a knife. Open the drum and let's find it.' How old was Jimmy?