Area {2,20}             Level 2             Area {3,30}
+-------------------+     +-----------------+     +--------------+
|                   |     |                 |     |              |
| S--RB27---Rx--Rz----RB2---Rb---Rc--Rd---Re--RB3---Rk--RB44---D |
|     27            |     |      39         |     |     44       |
|                 ----RB20---             ----RB30---            |
+-------------------+     +-----------------+     +--------------+