One Glass Brewery estimates the following activity for the coming year:

Expected production ............................................ 10 000 units
Expected direct labour hours ............................. 10 000 hours
Expected manufacturing overhead .......................... $100 000
Manufacturing overhead is allocated on the basis of direct labour hours.

At the end of the financial period the following information was collected:

Direct labour hours ....................................... 9000 hours
Manufacturing overhead ................................... $120 000

Required
(a) What was the predetermined manufacturing overhead rate calculated at the beginning of the year?
(b) What was the actual manufacturing overhead rate for the year?
(c) Explain the difference between the rates calculated in (a) and (b) above.