Which of the following is an example of an illusory promise? Gene promises to deliver $50$ units of a product every month as long the account with buyer is in good standing David agrees to mow the lawn every week if the weather permits. Sara promises to buy a car from Bob unless she decides she doesn't want $.$ Lisa commits to paying her rent on the first of the month by check or by Cashapp Mike agrees to paint a house as long as homeowner pays $$1,000.$