one more question

question:
as at 31 Dec 20×1, Red has tax adjusted losses of $4m which arose from a one-off restructuring exercise. Under tax law, these losses may be carried forward to relieve taxable profits in the future. Red has produced forecasts that predict total future taxable profits over the next three years of $2.5m. However the accountant of Red is not able to reliably forecast profits beyond that date.

The tax rate for profits earned during the year ended 31 Dec 20×1 is 30%. However, the government passed legislation during the reporting period that lowered the tax rate to 28% from 1 Jan 20×2.

explain the deferred tax implications of the above

my opinion : why do we have to use 28% ? answer says that we have to use 28% but the tax rate for profits earned during the year ended 31 Dec 20×1 so shouldnt we have to use 30% ????, 28% shd be used from 1 Jan 20×2 not 31 dec 20×1