Can you please explain how to solve this question?

Schlegel Department Store sells gift certificates-redeemable for store merchandise-that expire one year after their issuance. Schlegel has the following information pertaining to its gift certificates sales and redemptions: $ Unredeemed certificates at 12/31/17 2018 sales 2018 redemptions of prior year sales 2018 redemptions of current year sales 90,000 400,000 60,000 325,000 Schlegel's experience indicates that 10% of gift certificates will not be redeemed. The company's policy is to record revenue on gift certificates when they are redeemed or expire. Required: In its 2018 income statement, what amount should Schlegel report as gift certificate revenue