Please explain how you get the RETAINED EARNINGS

Blue Spruce Corp. began operations on January 1, 2017. The following information is avallable for Blue Spruce Corp. on December 31, 2017 $9,900 Notes payable 16,800 4,900 Accounts payable Accounts receivable Advertising expense Cash Common stock 6,900Rent expense 4,200Retained earnings 8,000 Service revenue 9,900Supplies 7,400 Supplies expense 31,700 Account Skills Via 4,800 6,800 1,500 Dividends Equipment