On its December 31, 2017 balance sheet, Calhoun Company appropriately reported a $10,000 debit balance in its Fair Value Adjustment account. There was no change during 2018 in the composition of Calhoun's portfolio of debt investments held as trading debt securities. The following information pertains to that portfolio:

SecurityCostFair value at 12/31/18

X$130,000$160,000

Y100,00090,000

Z175,000125,000

Total$405,000$375,000

How much should Calhoun debit (credit) to Unrealized holding gain/loss in 2018 related to this portfolio?

$40,000 debit

$40,000 credit.

$20,000 debit

$20,000 credit