I am reviewing can you explain this to me

Krier Corporation uses a predetermined overhead rate that was based on estimated manufacturing overhead of $738,000 and 30,000 direct labor-hours for the period. The company incurred actual manufacturing overhead of $792,000 and 31,500 total direct labor-hours during the period The manufacturing overhead for the period was: O $17,100 underapplied $17,100 overapplied O $54,000 underapplied O $54,000 overapplied