King Java's castle, shown in Figure 3-21, needs to be guarded. Write a GuardBot class to patrol the castle walls in the pattern shown. Be sure to use appropriate stepwise refinements. Choose an appropriate place for the guard to begin its duties. a. Write a main method that uses a single GuardBot to guard the castle. b. Write a main method that uses four GuardBots to patrol the castle, one on each side. c. Modify your solution so that all the guards patrol their wall simultaneously