Statements of Cash Flows (USD $)
| 6 Months Ended |
|---|
Sep. 30, 2011 | Sep. 30, 2010 |
|---|
| OPERATING ACTIVITIES | | |
| Net income | $ 5,994,321 | $ 6,307,107 |
| Adjustments to reconcile net income to net cash provided by operating activities: | | |
| Depreciation | 235,282 | 180,838 |
| Stock-based compensation | 80,160 | 76,720 |
| Deferred income taxes | (18,861) | (1,611) |
| Changes in operating assets and liabilities: | | |
| Accounts receivable | 624,700 | 83,146 |
| Inventories | (38,171) | (665,300) |
| Prepaid expenses and other assets | (169,689) | (291,882) |
| Accounts payable and accrued expenses | (324,240) | 41,826 |
| Deferred revenue | 0 | (20,833) |
| Net cash provided by operating activities | 6,383,502 | 5,710,011 |
| INVESTING ACTIVITIES | | |
| Purchases of fixed assets | (294,234) | (204,419) |
| Purchases of marketable securities | (9,504,221) | (7,765,811) |
| Proceeds from maturities and sales of marketable securities | 3,786,980 | 1,561,772 |
| Net cash used in investing activities | (6,011,475) | (6,408,458) |
| FINANCING ACTIVITIES | | |
| Net cash provided by financing activities | 0 | 0 |
| Increase (decrease) in cash and cash equivalents | 372,027 | (698,447) |
| Cash and cash equivalents at beginning of period | 952,209 | 1,389,288 |
| Cash and cash equivalents at end of period | 1,324,236 | 690,841 |
| Supplemental disclosures of cash flow information: | | |
| Cash (refunded) paid during the period for income taxes | $ 2,947,565 | $ 3,274,742 |