When has seller’s agent earned commission

A seller’s agent has earned his commission when:

  1.  he produces a buyer who signs a contract but later backs out
  2.  he produces a buyer who signs a contract and the entire deal goes through.
  3.  Only b.
  4.  Both a and b.

The answer is D – even if a buyer backs out, the agent has done the job he promised to do.  Of course, the agent may have to take legal action to get a commission in the scenario described by choice b.