On Monday morning Ethan sends a letter to Eva rejecting her offer to sell him her lawnmower, but a few hours later, Ethan changes his mind and sends a letter of acceptance to Eva. The letter of acceptance will be effective only if it is received by Eva before she receives the rejection.

Lawnmower

A machine utilizing one or more revolving blades to cut a grass surface to an even height.

Acceptance

The act of agreeing to an offer, or the acknowledgment of a deal's terms, making it legally binding.

Rejection

In contract law, the refusal to accept an offer or a breach by the other party, or in the context of goods, refusal because they do not meet specified terms.