Step by Step Problems No.4/Answer

Step 0              Step 1              Step 2              Step 3              Step 4
+---+---+---+---+   +---+---+---+---+   +---+---+---+---+   +---+---+---+---+   +---+---+---+---+
|       |   |   |   |       |   |   |   |       |   |   |   |       |   |   |   |       |   |   |
+       +   +   +   +       +   +   +   +       +   +   +   +       +   +   +   +       +   +   +
|       |   |   |   |       |   |   |   |       |   |   |   |       |   |   |   |       |   |   |
+---+---+---+---+   +---+---+---+---+   +---+---+---+---+   +---+---+---+---+   +---+---+---+---+
|   |   |XXX|XXX|   |   |   |   |XXX|   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
+---+---+---+---+   +---+---+   +---+   +---+---+   +   +   +---+---+   +   +   +---+---+   +   +
|       |   |   |   |       |   |   |   |       |   |   |   |       |   |   |   |XXX|XXX|   |   |
+---+---+   +   +   +---+---+---+   +   +---+---+---+---+   +---+---+---+---+   +---+---+---+---+
|       |   |   |   |       |XXX|   |   |       |XXX|XXX|   |XXX|XXX|       |   |       |       |
+---+---+---+---+   +---+---+---+---+   +---+---+---+---+   +---+---+---+---+   +---+---+---+---+

Step 5              Step 6              Step 7              Step 8              Step 9
+---+---+---+---+   +---+---+---+---+   +---+---+---+---+   +---+---+---+---+   +---+---+---+---+
|       |   |   |   |       |   |   |   |       |XXX|   |   |XXX|       |   |   |   |       |   |
+       +   +   +   +       +   +   +   +       +---+   +   +---+       +   +   +---+       +   +
|       |   |   |   |       |   |   |   |       |XXX|   |   |XXX|       |   |   |XXX|       |   |
+---+---+---+---+   +---+---+---+---+   +---+---+---+---+   +---+---+---+---+   +---+---+---+---+
|   |XXX|   |   |   |   |   |XXX|   |   |   |   |   |   |   |   |   |   |   |   |XXX|   |   |   |
+---+---+   +   +   +---+   +---+   +   +---+   +   +   +   +---+   +   +   +   +---+   +   +   +
|   |XXX|   |   |   |   |   |XXX|   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
+---+---+---+---+   +---+---+---+---+   +---+---+---+---+   +---+---+---+---+   +---+---+---+---+
|       |       |   |       |       |   |       |       |   |       |       |   |       |       |
+---+---+---+---+   +---+---+---+---+   +---+---+---+---+   +---+---+---+---+   +---+---+---+---+

Step 10             Step 11             Step 12             Step 13             Step 14
+---+---+---+---+   +---+---+---+---+   +---+---+---+---+   +---+---+---+---+   +---+---+---+---+
|   |       |   |   |   |       |   |   |   |       |   |   |   |       |   |   |   |       |XXX|
+---+       +   +   +---+       +   +   +---+       +   +   +---+       +   +   +---+       +---+
|   |       |   |   |   |       |   |   |   |       |   |   |   |       |   |   |   |       |XXX|
+---+---+---+---+   +---+---+---+---+   +---+---+---+---+   +---+---+---+---+   +---+---+---+---+
|XXX|   |   |   |   |   |XXX|   |   |   |   |   |XXX|   |   |   |   |   |XXX|   |   |   |   |   |
+---+   +   +   +   +   +---+   +   +   +   +   +---+   +   +   +   +   +---+   +   +   +   +   +
|XXX|   |   |   |   |   |XXX|   |   |   |   |   |XXX|   |   |   |   |   |XXX|   |   |   |   |   |
+---+---+---+---+   +---+---+---+---+   +---+---+---+---+   +---+---+---+---+   +---+---+---+---+
|       |       |   |       |       |   |       |       |   |       |       |   |       |       |
+---+---+---+---+   +---+---+---+---+   +---+---+---+---+   +---+---+---+---+   +---+---+---+---+

Step 15
+---+---+---+---+
|   |XXX|       |
+---+---+       +
|   |XXX|       |
+---+---+---+---+
|   |   |   |   |
+   +   +   +   +
|   |   |   |   |
+---+---+---+---+
|       |       |
+---+---+---+---+