o eree before the o eree makes an acceptance. Ar cle 478 An o er becomes invalid under any of the following circumstances: (1) the o er is rejected; (2) the o er is revoked in accordance with law; (3) the o eree makes no acceptance prior to expira on of the me limit for acceptance; or (4) the o eree materially alters the content of the o er. Ar cle 479 An acceptance is an expression of intent of the o eree to accept an o er. Ar cle 480 An acceptance shall be made by means of no ce, except that an acceptance may be made by performing an act according to the par es’ course of dealing or as indicated in the o er. Ar cle 481 An acceptance shall reach the o eror within the me limit speci ed in the o er. Where no me limit for acceptance is speci ed in the o er, an acceptance shall reach the o eror in accordance with the following provisions: (1) where an o er is made in a real- me communica on, acceptance shall be made promptly; or (2) where an o er is not made in a real- me communica on, the acceptance no ce shall reach the o eror within a reasonable period of me. Ar cle 482 Where an o er is made through a le er or a telegram, the me limit for acceptance shall be counted from the date shown on the le er or the date the telegram is handed in for dispatch or, if no such a date is shown on the le er, from the mailing date shown by the postmark of the le er. Where an o er is made by means of instantaneous communica ons such as telephone calls, facsimiles, or e-mails, the me limit for acceptance shall be counted from the moment the o er reaches the o eree. Ar cle 483 A contract is formed at the me when an acceptance becomes e ec ve, unless otherwise provided by law or agreed by the par es. Ar cle 484 Where an acceptance is made by means of no ce, the me when the acceptance becomes e ec ve shall be governed by the provisions of Ar cle 137 of this Code. Where an acceptance no ce is not required, the acceptance becomes e ec ve when an act of acceptance is performed according to the par es’ course of dealing or as indicated by the o er. Ar cle 485 An acceptance may be withdrawn. The provisions of Ar cle 141 of this Code shall apply to the withdrawal of an acceptance. Ar cle 486 Where an o eree makes an acceptance beyond the me limit for acceptance, or where the acceptance is made within the me limit for acceptance but it cannot reach the o eror in me under normal circumstances, such an acceptance cons tutes a new o er unless the o eror mely no es the o eree that the acceptance is e ec ve. Ar cle 487 Where an o eree makes an acceptance no ce within the me limit for acceptance, if the no ce would have reached the o eror in me under normal circumstances but reaches the o eror beyond the me limit for other reasons, the acceptance shall be e ec ve unless the o eror mely no es the o eree that the acceptance is not accepted as it exceeds the me limit for acceptance. Ar cle 488 The content of an acceptance shall be consistent with the content of the o er. Where the o eree proposes in the acceptance any material altera on to the content of the o er, it shall cons tute a new o er. An altera on concerning the object of the contract, the quan ty, quality, price or remunera on, me period of performance, place and manner of performance, default liability, the methods of dispute resolu on, or the like is a material altera on to the content of an o er. ti ti ff ff ff ti ff ti ff ti ff ff ti ti ti fi ff ti ff fi ff ff ti tt ff ff ti ti ff ff ti ff fi ti ti ff ff ff ti ti ff ti ti ti ti ff ti ff ti ti ti ti ff ff ti ti ti ff ff ti ti ff ti tt ti ti fi ff ti ti ti tt ti ti ti ti ti ti ti ti ff ti ff tt ff ti ff ff ff ff ff ff ti ti ff ff ff ff ti ti ti ti ti ti ti ti ti ti ti ti ff ff 53