Carnival Corporation is the largest cruise company in the world. The following item appears in the current liabilities section of it's balance sheet included in the Form 10-K for the year ended November 30, 2015:

Customer deposits ......................................................... $3,272 million

In addition, Note 2 to the financial statements includes the following:

Revenue and Expense Recognition

Guest cruise deposits represent unearned revenues and are initially included in customer deposit liabilities when received. Customer deposits are subsequently recognized as cruise revenues, together with revenues from onboard and other activities, and all associated direct costs and expenses of a voyage are recognized as cruise costs and expenses, upon completion of voyages with durations of ten nights or less and on a pro rata basis for voyages in excess of ten nights....

Required

1. What economic event caused Carnival to incur this liability? Was it an external or internal event?

2. Describe the effect on the accounting equation from the transaction to record the customer deposits.

3. Assume that one customer makes a deposit of $1,000 on a future cruise. Determine the effect on the accounting equation from this transaction.

4. What economic event will cause Carnival to reduce its customer deposits liability? Is this an external or internal event?