law: Indian Contract Act, 1872 
  7. Acceptance must be absolute
  In order to convert a proposal into a promise the acceptance
  
  must-
  (1) be absolute and unqualified.
  (2) be expressed in some usual and reasonable manner, unless the
  
  proposal prescribes the manner in which it is to be accepted. If the proposal
  
  prescribes a manner in which it is to be accepted, and the acceptance is not
  
  made in such manner, the proposer may, within a reasonable time after the
  
  acceptance is communicated to him, insist that his proposal shall be accepted
  
  in the prescribed manner, and not otherwise; but, if he fails to do so, he
  
  accepts the acceptance.