If I entered into an agreement with you to sell you 10 phones, and we agreed that I will deliver you 1 phone a week, and thus all phones will be delivered to you after 10 weeks, my question is, first, our agreement is an agreement to sell, right? and once I have passed you a phone, does it amount to a "sale"? or our agreement to sell only becomes a sale after all phones have been passed to you? Thank you!