Let R be the region bounded by<img src="https://static.zxtiku.com/wangke/imgs/topic/bdbae402b9e6c982d840087ffd4bd79f.png"/>, y=2, y=6 and x=0. The volume of the solid obtained when R is revolved about the y-axis is<img src="https://static.zxtiku.com/wangke/imgs/topic/bc6d18a7acf4a88e886cc9001f51bd95.png"/>