(1) Unless otherwise unambiguously indicated by the language or circumstances:

(a) An offer to make a contract shall be construed as inviting acceptance in any manner and by any medium reasonable in the circumstances;

(b) An order or other offer to buy goods for prompt or current shipment shall be construed as inviting acceptance either by a prompt promise to ship or by the prompt or current shipment of conforming or nonconforming goods, but such a shipment of nonconforming goods does not constitute an acceptance if the seller seasonably notifies the buyer that the shipment is offered only as an accommodation to the buyer.

(2) Where the beginning of a requested performance is a reasonable mode of acceptance an offeror who is not notified of acceptance within a reasonable time may treat the offer as having lapsed before acceptance.