• Object: Complete the problems in 3.11.
• Create a directory named ``pup4'' under your home directory.
  This directory must contain
  • Makefile
  • README
  • other files..
• When type ``make'' in your exercise directory, three executables named showtreesize, mydu, and mydub are created. The output of the last one which uses the breadth_first_apply function is similar to example 3.30 (page 128).
• The file ``README'' contains your description of your exercise. Your description should explain briefly how you solve the 6 subproblems. For example, for subproblem 1, you should, at least, let me know which file containing your isadirectory().
• Due day, 4/1 00:01am