Revert "Delete plot4.png"

This reverts commit dfecaa0453435a290ad2de49f94526496e18d816.
Revert "Delete plot3.png"

This reverts commit ae74ff2ea530fcc9abf27c804e5b7ad5dd37febf.
Revert "Delete plot2.png"

This reverts commit 418bfe6b5f1627a10c2d1e45ab15a6f252bf1e19.