On 31 December, the end of the accounting period of Ultra Corp., the company accountant is about to make some adjustments. Describe a set of circumstances where, in making the typical year-end adjustments: 

a. An expense is debited and a liability is credited 

b. An expense is debited and an asset contra account is credited 

c. An asset is debited and revenue is credited d a liability is debited and revenue is credited.