How do you get the cannon to world 4 in new Super Mario Bros?

New super Mario bros world 5 cannon.

In the World 5 ghosthouse.

On the staircase there will be a boxer.

There will be a flights of stairs on the right,you will see 3 blocks on the left. Jump on them, then jump up again on each block to reveal another 3 blocks. Then jump on the middle one that you revealed and jump up again. There will be a beanstalk that willl take you up to a door where a boxer will be. It will need to punch some blocks so you can get to the door. But when it falls be aware that it doesn't hit you. Through the door will be a red flag. You should now be able to use the warp cannon on world 5.

This cannon will take you to World 8.