EXHIBIT 10.16

December 18,
2002

Mr. Robert
J. Weiskopf
Corporate Controller
Lightbridge, Inc.
67 South Bedford Street, Suite 100E
Burlington, MA 01803

Dear
Mr. Weiskopf:

The
following summarizes the revised terms that we agreed to on December 11, 2002 regarding the $1,722,417 million promissory note, as amended, that Wireless Billing Systems, d.b.a.
Primal Billing Solutions ("PBS"), a wholly-owned subsidiary of Primal Solutions, Inc. owes to Corsair (a Lightbridge subsidiary):



Please
indicate your acceptance of these terms by signing below.

|Agreed and accepted:                                      |                                      |                   |    
|--------------------------------------------------------- | ------------------------------------ | ----------------- | ---
|Wireless Billing Systems,
d.b.a. Primal Billing Solutions |                                      | Lightbridge, Inc.
|By:                                                       | /s/WILLIAM SALWAYWilliam Salway, CEO |                   | By:

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Primal Promissory Note to Lightbridge, Inc.  Amortization Schedule

|   |  |          |  |             |  |              |  |              |  | interest rate |  | 8%          
|-- |  | -------- |  | ----------- |  | ------------ |  | ------------ |  | ------------- |  | ------------
|
|
|1  |  | 1/26/03  |  |             |  | 1,722,417.00 |  | 25,000.00    |  | 11,482.78     |  | 13,517.22   
|2  |  | 2/26/03  |  |             |  | 1,708,899.78 |  | 25,000.00    |  | 11,392.67     |  | 13,607.33   
|3  |  | 3/26/03  |  |             |  | 1,695,292.45 |  | 25,000.00    |  | 11,301.95     |  | 13,698.05   
|4  |  | 4/26/03  |  |             |  | 1,681,594.39 |  | 25,000.00    |  | 11,210.63     |  | 13,789.37   
|5  |  | 5/26/03  |  |             |  | 1,667,805.02 |  | 25,000.00    |  | 11,118.70     |  | 13,881.30   
|6  |  | 6/26/03  |  |             |  | 1,653,923.72 |  | 25,000.00    |  | 11,026.16     |  | 13,973.84   
|7  |  | 7/26/03  |  |             |  | 1,639,949.88 |  | 25,000.00    |  | 10,933.00     |  | 14,067.00   
|8  |  | 8/26/03  |  |             |  | 1,625,882.88 |  | 25,000.00    |  | 10,839.22     |  | 14,160.78   
|9  |  | 9/26/03  |  |             |  | 1,611,722.10 |  | 25,000.00    |  | 10,744.81     |  | 14,255.19   
|10 |  | 10/26/03 |  |             |  | 1,597,466.91 |  | 25,000.00    |  | 10,649.78     |  | 14,350.22   
|11 |  | 11/26/03 |  |             |  | 1,583,116.69 |  | 25,000.00    |  | 10,554.11     |  | 14,445.89   
|12 |  | 12/26/03 |  |             |  | 1,568,670.81 |  | 25,000.00    |  | 10,457.81     |  | 14,542.19   
|13 |  | 1/26/04  |  |             |  | 1,554,128.61 |  | 25,000.00    |  | 10,360.86     |  | 14,639.14   
|14 |  | 2/26/04  |  |             |  | 1,539,489.47 |  | 25,000.00    |  | 10,263.26     |  | 14,736.74   
|15 |  | 3/26/04  |  |             |  | 1,524,752.73 |  | 25,000.00    |  | 10,165.02     |  | 14,834.98   
|16 |  | 4/26/04  |  |             |  | 1,509,917.75 |  | 25,000.00    |  | 10,066.12     |  | 14,933.88   
|17 |  | 5/26/04  |  |             |  | 1,494,983.87 |  | 25,000.00    |  | 9,966.56      |  | 15,033.44   
|18 |  | 6/26/04  |  |             |  | 1,479,950.43 |  | 25,000.00    |  | 9,866.34      |  | 15,133.66   
|19 |  | 7/26/04  |  |             |  | 1,464,816.76 |  | 25,000.00    |  | 9,765.45      |  | 15,234.55   
|20 |  | 8/26/04  |  |             |  | 1,449,582.21 |  | 25,000.00    |  | 9,663.88      |  | 15,336.12   
|21 |  | 9/26/04  |  |             |  | 1,434,246.09 |  | 25,000.00    |  | 9,561.64      |  | 15,438.36   
|22 |  | 10/26/04 |  |             |  | 1,418,807.73 |  | 25,000.00    |  | 9,458.72      |  | 15,541.28   
|23 |  | 11/26/04 |  |             |  | 1,403,266.45 |  | 25,000.00    |  | 9,355.11      |  | 15,644.89   
|24 |  | 12/26/04 |  |             |  | 1,387,621.56 |  | 25,000.00    |  | 9,250.81      |  | 15,749.19   
|   |  |          |  |             |  |              |  |              |  |               |  |             
|   |  |          |  |             |  |              |  | 600,000.00   |  | 249,455.37    |  | 350,544.63  
|24 |  | 12/26/04 |  |             |  | 1,371,872.37 |  | 1,371,872.37 |  |              |  | 1,371,872.37
|   |  | 12/26/04 |  | Balance Due |  |             |  |              |  |               |  |             

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