Urgent help on accounting homework please?

Prepare any necessary adjusting or correcting entries called for by the following situations. Assume that no entries have been made regarding the situation other than those specifically described. Consider each situation separately.

a. Machinery is repaired and maintained by an outside maintenance company on an annual fee basis, payable in advance. The $1,200 fee was paid in advance on October 1 (for 12 months beginning October 1) and was charged to Rent Expense. What adjustment is necessary on December 31?

b. On June 1, $10,000 of machinery was purchased. $400 cash was paid down and a 3-month, 10% note payable was signed for the balance. The June 1 transaction was properly recorded. Prepare the adjustment for the interest as of June 30.

c. On August 1, $1,600 was paid in advance to the landlord for two month's rent. The tenant debited Prepaid Rent for $1,600 on August 1. What adjustment is necessary as of August 31?