Final answer:
Rock Corp. should credit its year 9 other comprehensive income by $25,000 due to the $15,000 recovery of value from the prior year's decline and the additional $10,000 increase in the market value of their available-for-sale securities.
Step-by-step explanation:
The student has asked about the adjustment to other comprehensive income due to the changes in market value of available-for-sale securities at Rock Corp. Since the company does not elect the fair value option, the increase in market value from year 8 to year 9 would be recorded in other comprehensive income. At the end of year 8, the securities were valued at $65,000, which was $15,000 below cost.
However, by the end of year 9, the market value increased to $90,000, which is $10,000 above cost. Therefore, Rock Corp. should increase (credit) its year 9 other comprehensive income by $25,000 - which is the $15,000 recovery of the previous year's decline, plus the $10,000 additional increase in value.