(1) The acceptance of a bill is the signification by the drawee of his assent to the order of the drawer.
(2) An acceptance is invalid unless it complies with the following conditions, namely:
(a) It must be written on the bill and be signed by the drawee. The mere signature of the drawee without additional words is sufficient.
(b) It must not express that the drawee will perform his promise by any other means than the payment of money.