Four conditions must be met before revenue should be recognized. In each of the following cases, tell which condition has not been met:

a. Company A accepts a contract to perform services in the future for $1 ,000.

b. Company B ships products to another company worth $1 ,500 without an order from the other company but tells the company that it can return the products if it does not sell them.

c. Company C performs services for $5,000 for a company that is in financial difficulty.

d. Company D agrees to work out a price later for services that it performs for another company.