✔ 最佳答案
This question is very interesting.
1) My first idea comes from your last question: "請問A可以告B違約?" Should we present in its converse as "請問B可以告A違約?" It is because A has no lose and he has enjoyed the service provided by B. The victim seems to be B and B should be the one who accuse against A.
2) Your another sentense is abouut A: "邊搖頭一邊話好,我接受你提出的offer". Here the real gesture of A was unseen and we cannot judge from here whether he smiled, laughed or angered when he spoke the message. We cannot judge from his tone whether he is speaking the converse.
3) Nevertheless, if we do not regard the conversation environment and simply concentrate on "A接受B提出的offer" then if B has finished the task with satisfaction, A should refer to the agreement and provide B the book as the gift.
4) I used the word "satisfaction" above because if B did not really complete the task ( i.e. incomplete ) then B has not finished what he promised and A has the right to turn down his request. There is a controversial area for arguments.
5) If B has really completed the task, then even they have not signed a paperwork agreement, their verbal agreement is still regarded as valid under HK legislation system. B can accuse A for his failure to provide the book and seek for compensation.
6) Of course, if B suits A, both are losers for there is large amount of money used on lawsuits.
Hope I can answer your question with logical points.
參考: Mathematics Teacher Mr. Ip