Identify the accounting concept or principle that gives the most direction on how to account for each of the following situations:

a. A customer states her intention to switch travel agencies. Should the new travel agency record revenue based on this intention?

b. The owners of a business desire monthly financial statements to measure the progress of the entity on an ongoing basis.

c. Expenses of the period total \(\$ 6,100\). This amount should be subtracted from revenue to compute the period's income.

d. Expenses of \(\$ 2,800\) must be accrued at the end of the period to measure income properly.