At the beginning of 20X1, a company had prepaid rent of $2,400 for 3 months. When the rental agreement was renewed, the company paid $12,000 for one year. At that time the company debited prepaid rent for $12,000 and credited cash for $12,000. This was the only entry made during the year with regard to rent. What would be the adjusting entry on December 31, 20X1?