to our investment custodian.  Most of our cash equivalents and marketable securities are valued based on Level 2 inputs.  As of January 30, 2011, we collected the balance of our investment in the Reserve International Liquidity Fund, Ltd., or International Reserve Fund, that was classified as a Level 3 input due to the inherent subjectivity and the significant judgment involved in its valuation. As such, we do not have any investment classified as Level 3 as of January 30, 2011.



      All of our available-for-sale investments are subject to a periodic impairment review. We record a charge to earnings when a decline in fair value is significantly below cost basis and judged to be other-than-temporary, or have other indicators of impairments.  If the fair value of an available-for-sale debt instrument is less than its amortized cost basis, an other-than - temporary impairment is triggered in circumstances where (1) we intend to sell the instrument, (2) it is more likely than not that we will be required to sell the instrument before recovery of its amortized cost basis, or (3) a credit loss exists where we do not expect to recover the entire amortized cost basis of the instrument. If we intend to sell or it is more likely than not that we will be required to sell the available-for-sale debt instrument before recovery of its amortized cost basis, we recognize an other-than- temporary impairment in earnings equal to the entire difference between the debt instruments’ amortized cost basis and its fair value.  For available-for-sale debt instruments that are considered other-than-temporarily impaired due to the existence of a credit loss, if we do not intend to sell and it is more likely than not that we will be required to sell the instrument before recovery of its remaining amortized cost basis (amortized cost basis less any current-period credit loss), we separate the amount of the impairment into the amount that is credit related and the amount due to all other factors.  The credit loss component is recognized in earnings.

 

          Stock-based Compensation

 

         Our stock-based compensation cost for equity awards is measured at grant date, based on the fair value of the awards, and is recognized as expense over the requisite employee service period.  We recognize stock-based compensation expense using the straight-line attribution method.  We estimate the fair value of employee stock options on the date of grant using a binomial model and we use the closing trading price of our common stock on the date of grant as the fair value of awards of restricted stock units, or RSUs.  The determination of fair value of share-based payment awards on the date of grant using an option-pricing model is affected by our stock price as well as assumptions regarding a number of highly complex and subjective variables. These variables include, but are not limited to, the expected stock price volatility over the term of the awards, actual and projected employee stock option exercise behaviors, vesting schedules, death and disability probabilities, expected volatility and risk-free interest. Our management has determined that the use of implied