Are they really that hard that are beyond your power of understanding...?
Besides,this guy didn't solve them as part of his class preparation during PhD:
Disclaimer: These "solutions" are my own personal unprofessional attempts at solving the problems. They are officially sanctioned neither by the textbook authors nor by anybody else in particular, they have for the most part not been checked for errors, and, if past precedent is any guide, there is every reason to believe that many of them are dead wrong
Daniel.