Determine the amount of retained earnings

Question

Balance Sheet Preparation with a Missing Element
The following data are available for Schubert Products Inc. as of December 31, 2012.

1. Cash  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . $  7,500
2. Accounts payable . . . . . . . . . . . . . . . . . . . . . . . 24,000
3. Capital stock. . . . . . . . . . . . . . . . . . . . . . . . . . . 42,000
4. Accounts receivable  . . . . . . . . . . . . . . . . . . . . . 20,000
5. Building  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49,500
6. Supplies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2,000
7. Retained earnings . . . . . . . . . . . . . . . . . . . . . . .       ?      
8. Land. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20,000

Required:
1. Prepare a balance sheet for Schubert Products Inc.
2. Determine the amount of retained earnings at December 31, 2012.
3.  Interpretive Question: In what way is a balance sheet a depiction of the basic accounting equation?