Barbara intends to sell her motorcycle for $$2,500.$ When she learns that Lee is interested in buying a used motorcycle, she sends him an e$-$mail offering to sell the motorcycle to him. When typing the e$-$mail, however, she mistakenly keys in the price of $$1,500.$ Lee immediately sends Barbara an e$-$mail reply accepting her offer to buy the motorcycle. Lee then sends Barbara a Venmo payment for $$1,500.$ Barbara replies and indicates she actually meant $$2,500.$ Lee is upset. What is this an example of$,$ and is this a valid contract?