XYZ Company applies overhead to jobs using direct labor cost as an activity. For the current year, XYZ's estimated overhead was $144,000 while the actual overhead cost totaled $136,000. For the current year, XYZ's estimated direct labor cost was $240,000 and its actual direct labor cost amounted to $220,000. For the year, overhead was:

a. over-applied by $6,800
b. over-applied by $4,000
c. over-applied by $8,000
d. under-applied by $6,800
e. under-applied by $4,000
f. under-applied by $8,000