During 2015, these prepaid product lines generated revenue of $4662 million, and AT&T reported the following deferred revenue liability on its December 31 2015, balance sheet. 1. What economic rationale can we provide to explain why AT&T offers prepaid services? 2. Use the balance sheet information and the total revenue for 2015 to determine the total amount of cash collected from prepaid customers during 2015. 3. If AT&T gift cards have no expiration date, when, if ever, would the company record revenue on the cards? Explain.